Upgrading to an APR exhaust system on your Mitsubishi 3000GT VR4 is one of the most effective bolt-on modifications for unlocking extra horsepower and improving the driving experience. Enthusiasts have reported gains of up to 20 horsepower at the wheels when pairing a properly tuned APR system with the stock turbochargers and engine management. This comprehensive guide walks you through every step of the installation, from gathering the right tools to performing a final leak check. We’ll cover removal of the factory exhaust, proper fitment of the APR components, torque specifications, and tips to avoid common pitfalls. By the end, you’ll have the confidence to complete the install yourself and enjoy the sound and performance benefits that come with a free-flowing exhaust.

Understanding the APR Exhaust System and Its Benefits

The APR exhaust system for the 3000GT VR4 is a cat-back (or turbo-back) aftermarket replacement designed to reduce back pressure and improve exhaust gas flow. Unlike the restrictive factory system with its multiple resonators and small-diameter tubing, APR’s mandrel-bent pipes and high-flow mufflers allow the twin-turbo V6 to expel gases more efficiently. This reduction in restriction translates directly into increased horsepower (up to 20 hp), improved throttle response, and a deeper, more aggressive exhaust note.

Beyond the power gain, the APR system reduces weight by approximately 15–20 pounds compared to the stock exhaust, which helps with overall vehicle balance and acceleration. The stainless steel construction also provides superior corrosion resistance, ensuring the system lasts for years even in harsh climates. For those planning further modifications—such as upgraded intercoolers, larger turbos, or a standalone ECU—the APR exhaust lays a solid foundation by minimizing back pressure from the outset.

Tools and Materials You’ll Need

Before you begin, gather all necessary tools and supplies. Having everything on hand prevents unnecessary trips to the hardware store and keeps the workflow smooth.

  • APR exhaust system (complete kit: downpipe, midpipe, muffler section, hardware, gaskets)
  • Socket set (metric, 10mm–19mm; deep sockets recommended)
  • Wrench set (combination and ratcheting wrenches in metric sizes)
  • Breaker bar (1/2-inch drive for stubborn bolts)
  • Torque wrench (ft-lb and in-lb ranges)
  • Jack and jack stands (minimum 2-ton capacity each)
  • Penetrating oil (e.g., PB Blaster or Liquid Wrench)
  • Wire brush or sandpaper (for cleaning flange surfaces)
  • Exhaust gaskets (new; usually included with kit, but buy OEM if not)
  • Anti-seize compound (for bolt threads)
  • Safety glasses and gloves
  • Shop rags and a drop cloth (to catch debris)
  • Lubricant spray (WD-40 or similar for rubber hangers)
  • Flathead screwdriver or pry bar (for removing hanger rings)

Preparation and Safety

Lifting the Vehicle

Park your 3000GT VR4 on a level, solid surface. Engage the parking brake and chock the front wheels. Using a hydraulic jack, lift the rear of the vehicle at the designated jack point (the rear differential or reinforced subframe rail). Secure the car on jack stands placed under the rear subframe or frame rails. Never rely on the jack alone. Double-check that the vehicle is stable before crawling underneath.

Cool Down and Access

Allow the exhaust system to cool completely if the car was driven recently. Hot exhaust components can cause severe burns. Wear safety glasses and gloves throughout the process. If you have sensitive skin or prefer extra protection, consider using a mechanic’s suit or long sleeves.

Removing the Factory Exhaust System

Removing the stock exhaust from a 3000GT VR4 can be challenging due to years of heat cycling and corrosion. The following steps break the process into manageable stages.

Step 1: Apply Penetrating Oil

Generously spray all exhaust bolts, nuts, and studs with penetrating oil. Pay special attention to the flange connections at the catalytic converter (or turbo outlet for turbo-back systems), the midpipe hangers, and the muffler section. Allow the oil to soak for at least 10–15 minutes. For heavily seized bolts, reapply and wait longer.

Step 2: Disconnect the Exhaust Hangers

The factory exhaust is supported by rubber hangers that fit into metal brackets. Use a flathead screwdriver or pry bar to work the rubber rings off the studs. If they are stiff, spray them with lubricant to facilitate removal. Be careful not to tear the rubber—though you won’t reuse them, having intact hangers makes removal easier.

Step 3: Unbolt the Exhaust Sections

Starting at the rear of the vehicle, work forward:

  • Muffler section: Remove the bolts connecting the muffler to the midpipe (typically two bolts or a clamp). Carefully lower the muffler from its hanger and set aside.
  • Midpipe: Unbolt the midpipe from the catalytic converter flange. The joint may use a spring-loaded bolt design; note the orientation of the springs for reassembly. If the bolts resist, use the breaker bar.
  • Downpipe (if replacing): For a full turbo-back system, you’ll need to unbolt the downpipe from the turbo outlet. This step requires access from both above and below the car. A swivel socket is helpful. If the downpipe has a separate catalytic converter, remove that as well.

Step 4: Maneuver the Old Exhaust Out

With all connections free, slide the exhaust sections out from under the car. An extra set of hands helps to avoid scratching the underbody or bumping the O2 sensors. Carefully inspect the old system for any broken or missing hangers that might still be attached to the vehicle; remove them with pliers or a pry bar.

Installing the APR Exhaust System

Before bolting in the APR system, thoroughly clean all flange surfaces on the vehicle (catalytic converter, turbo outlet, or any remaining intermediate pipe). Use a wire brush or sandpaper to remove rust, gasket material, and carbon deposits. New gaskets are essential for a leak-free connection.

Step 1: Fit the APR Downpipe (if applicable)

If your kit includes a downpipe, install it first. Apply a thin coat of anti-seize to the studs/bolts that connect to the turbo. Position the new gasket and gently hand-tighten the bolts. Do not fully torque yet—leave slight play to allow alignment with the midpipe.

Step 2: Assemble the Midpipe and Muffler Section

Connect the APR midpipe to the downpipe or catalytic converter flange using the supplied gasket and hardware. Hand-tighten the bolts. Then, attach the muffler section to the midpipe using the slip joint or flanged connection. Some APR systems use band clamps; ensure the clamp is positioned squarely over the joint before tightening.

Step 3: Install Hangers

Insert the supplied hanger rods or rubber isolators into the exhaust brackets. The 3000GT VR4 has multiple mounting points along the tunnel and at the rear. If your APR kit uses different hanger positions than the stock setup, follow the manufacturer’s instructions. Lubricate the hanger bushings with soapy water to make them slide on easily.

Step 4: Align and Tighten

With all components loosely connected, check the alignment. The exhaust should hang evenly without contacting the underbody, driveshaft, or sway bar. Adjust as needed by shifting sections or repositioning hangers. Once alignment is satisfactory, torque all flange bolts to the manufacturer’s specification (typically 30–40 ft-lb for 10mm bolts, but always verify). Use a torque wrench to ensure uniformity and prevent overtightening, which can strip threads or warp flanges.

Step 5: Final Torque and Check

Double-check every bolt and clamp. Pay particular attention to the downpipe-to-turbo connection if equipped. For V-band clamps, tighten until the clamp seats fully. For spring-loaded bolts, use a torque wrench to tighten until the spring is compressed to the specified length (refer to APR’s manual).

Post-Installation Checks and Test Drive

Visual Inspection

Look for any exhaust contact with the car’s body, heat shields, or suspension components. Turn the steering wheel to full lock to ensure clearance. Jiggle the exhaust by hand to check for movement-induced contact.

Leak Test

Start the engine with the car still on jack stands (parking brake engaged). Listen for hissing noises around each joint and flange. A shop rag held near the connection can help detect puffs of air. If a leak is suspected, tighten the bolts slightly or re-seat the gasket. Minor leaks can be cured with exhaust sealant, but a proper mechanical connection is preferable.

Sound and Performance

Allow the engine to reach operating temperature. The APR system will sound louder than the stock exhaust, with a deeper tone that becomes aggressive under load. Let the idle stabilize; the ECU may adjust fuel trims. Do not be alarmed if the exhaust note changes as the system breaks in over the first 100 miles.

Test Drive

Lower the vehicle and take it for a careful test drive. Accelerate moderately to verify smooth power delivery. Listen for any drone or buzz at highway speeds. Some resonance is normal, but pronounced rattling indicates contact. Re-inspect the hangers and clearance after the drive while components are warm.

ECU Adaptation

The 3000GT VR4’s ECU will learn the new exhaust flow over time. If you also installed a free-flowing downpipe, consider a ECU tune to fully realize the 20 hp gain. Without a tune, the stock ECU may not advance timing optimally, but the power increase will still be noticeable. For maximum results, consult a professional tuner or use a flash tool like ECUFlash to adjust fuel and timing maps.

Troubleshooting Common Issues

Rusted or Seized Bolts

If bolts break during removal, use a bolt extractor or carefully drill out the remnants. Replace with high-strength hardware (Grade 8 or stainless). Apply anti-seize to prevent future seizing.

Exhaust Hanging Too Low

Adjust hanger angles or consider using shorter hanger bushings. Some APR kits include adjustable hooks. Ensure the exhaust is not pulling on the hanger too tightly.

Check Engine Light

If you deleted the catalytic converter, you may get a P0420 code. Install a spark plug non-fouler or an oxygen sensor spacer on the rear O2 sensor to eliminate the code. Alternatively, have the code tuned out.

Drone at Cruise

APR systems are designed to minimize drone, but some resonance may occur. Adding a resonator or using a Helmholtz chamber can reduce specific frequencies. Ensure all clamps are tight to prevent vibration.

Performance Gains: What to Expect

When installed correctly on a healthy 3000GT VR4, an APR exhaust system combined with a free-flowing downpipe and a modest ECU tune can yield 20–25 wheel horsepower. Without a tune, expect closer to 12–15 hp. The torque curve also improves, delivering stronger mid-range pull. The sound upgrade alone makes the effort worthwhile, but the real reward is the car’s sharper response to throttle inputs.

Maintenance Tips for Longevity

  • Periodically check bolts and clamps for tightness, especially after the first 500 miles.
  • Clean the exhaust tips with metal polish to prevent discoloration.
  • Inspect rubber hangers annually; replace if cracked or brittle.
  • If the car is driven in winter, rinse the underside to remove road salt that can accelerate corrosion.

Additional Resources

For detailed torque specifications and part diagrams, consult the factory service manual for your 3000GT VR4. The 3SI.org forums have extensive threads on exhaust installations and user experiences. Also, visit NABR (North American Boosted Rocketry) for community support and tuning advice. If you need the APR product manual, check the manufacturer’s official website or contact their support team.

Conclusion

Installing an APR exhaust system on your 3000GT VR4 is a rewarding project that unlocks measurable horsepower, reduces weight, and transforms the car’s auditory character. With the right tools, careful preparation, and attention to detail, you can complete the job in an afternoon and immediately enjoy the benefits. Whether you are a seasoned enthusiast or a first-time modifier, the process outlined above will help you achieve a professional-grade installation. After the final bolt is torqued and the car comes off the jack stands, you’ll appreciate the renewed vitality that a free-flowing exhaust brings to Mitsubishi’s iconic twin-turbo legend.