Introduction: Why Install an AWE Tuning Cold Air Intake on Your B5 S4?

The B5 S4, with its iconic 2.7-liter twin-turbo V6, remains a favorite among enthusiasts for its tuning potential and robust engineering. One of the first and most rewarding upgrades is a cold air intake (CAI) system. The AWE Tuning Cold Air Intake is specifically designed for the C5 platform (B5 S4 and RS4), offering a direct fit with no modification required. It not only increases airflow to the turbos, reducing intake restriction, but also delivers a more aggressive induction sound that makes every throttle blip more exciting. This guide covers every detail of the installation process, from tools needed to post-install checks, ensuring a smooth, successful upgrade that yields measurable performance gains.

Benefits of the AWE Tuning Cold Air Intake on a B5 S4

  • Reduced intake restriction – The stock airbox is notoriously restrictive, especially when paired with higher boost levels. The AWE kit uses a large, high-flow conical filter and smooth mandrel-bent aluminum tubing to minimize pressure drop.
  • Intake air temperature reduction – The system draws cooler air from the front of the engine bay, away from the heat of the turbos, which helps prevent heat soak and maintains denser air for combustion.
  • Improved throttle response and sound – Many drivers report a noticeably sharper throttle tip-in and a deeper, more aggressive intake roar when the turbos spool.
  • Essential for stage 1 and 2 tuning – Most B5 S4 software upgrades (APR, Unitronic, GIAC, etc.) require or strongly recommend a free-flowing intake to achieve their stated horsepower and torque gains.
  • Reusable, washable filter – The included oiled cotton gauze filter can be cleaned and re-oiled, making it a long-term, cost-effective upgrade compared to disposable paper filters.

Tools and Materials Needed

  • AWE Tuning Cold Air Intake Kit (includes filter, tubing, couplers, clamps, brackets, and hardware)
  • Socket set with extensions – 10mm, 13mm sockets, ¼” drive recommended
  • Flathead screwdriver – for prying hose clips and loosening slotted clamps
  • Phillips screwdriver – #2 size
  • Torque wrench (5–15 lb-ft range for small fasteners)
  • Rubber gloves – to keep hands clean and prevent oil from contaminating the MAF sensor
  • Clean shop towels or rags – for wiping oil residue and catching any loose bolts
  • Optional but helpful: trim removal tool, magnetic pickup tool, flashlight, ¼” drive ratchet with universal joint for tight spaces

Preparation: Safety and Workspace

Park the vehicle on a level surface and allow the engine to cool completely. Disconnect the negative battery terminal to prevent any electrical short or accidental airbag deployment. Remove the engine cover if present (B5 S4s may have a cosmetic cover over the intake system). Gather all tools and keep the AWE kit components within easy reach. Lay out the installation instructions provided by AWE Tuning, noting any specific torque values or orientation marks. If you are working on a car with a stock or aftermarket boost controller, ensure the area is free from flammable materials.

Step 1: Remove the Engine Cover (if equipped) and Factory Air Intake Snorkel

Using a 10mm socket, remove the four bolts holding the plastic engine cover. Gently lift the cover upward and set it aside. Next, locate the factory plastic intake snorkel that runs from the front grille to the airbox. Squeeze the release tabs and pull the snorkel inward to detach it. Some B5 S4s have a secondary resonator box attached to the snorkel – you can remove it entirely once the new intake is installed.

Step 2: Disconnect the Mass Air Flow (MAF) Sensor and Factory Intake Tube

The MAF sensor is located on the factory intake tube between the airbox and the throttle body. Unplug the electrical connector by pressing the locking tab and pulling firmly on the connector body, not the wires. Be careful not to damage the MAF element – avoid touching it with tools or fingers. Use a flathead screwdriver to loosen the two adjustable stainless steel clamps holding the intake tube to the turbo inlet hoses. Slide the clamps back and gently twist the tube to break the seal, then pull the tube free. Set it aside.

Step 3: Remove the Factory Air Box Assembly

The lower portion of the airbox is secured by one 13mm bolt on the passenger side (near the inner fender) and two 10mm bolts at the base. On some models, there is also a rubber grommet that needs to be pushed through. Remove all fasteners and carefully lift the airbox out of the engine bay. You may need to tilt it slightly to clear the auxiliary coolant tank and power steering reservoir. Discard the airbox or store it if you plan to revert to stock.

Step 4: Install the AWE Tuning Cold Air Intake Bracket and Filter Housing

The AWE kit includes a laser-cut aluminum bracket that mounts to the original airbox mounting points. Use the supplied hardware (M6 bolts and washers) to affix the bracket. Torque to 8 lb-ft. Then, loosely mount the AWE intake tube and filter housing to the bracket. Do not tighten yet – leave all clamps and fasteners finger‑tight to allow adjustment later. Position the large conical filter so that it sits behind the driver-side headlight (for the B5 S4) and is not obstructed by the coolant hose or wiring harness. The AWE filter is pre-oiled, but you should double‑check that no excess oil is present on the filter mesh – too much oil can contaminate the MAF sensor.

Step 5: Connect the AWE Intake Tube to the Turbos’ Inlet Hoses

The AWE kit uses a silicone coupler and T‑bolt clamps to connect the intake tube to the stock turbo inlet hoses. Slide the coupler over each turbo inlet hose (one per hose) and loosely tighten. Insert the larger end of the AWE aluminum tube into the coupler. Adjust the final position of the tube so it sits parallel to the engine and does not rub against the engine block or wiring. Once aligned, tighten the T‑bolt clamps to 6 lb‑ft – do not overtighten, as it may damage the silicone coupler. Ensure the clamps are oriented for easy access with a screwdriver or socket.

Step 6: Reinstall the MAF Sensor into the AWE Intake Tube

Locate the MAF sensor port on the AWE intake tube (it has a small raised boss). Clean the rubber O‑ring on the MAF sensor with a lint‑free cloth – avoid using solvents. Lightly lubricate the O‑ring with silicone grease (provided or purchased separately) to prevent tearing. Insert the sensor into the port so the wiring harness connector faces upward (matching the factory orientation). Secure the sensor with the two factory screws (or the supplied M4 bolts) and torque to 3 lb‑ft (hand‑tight is sufficient). Reattach the electrical connector: push until you hear a click, then gently tug to verify it is locked.

Step 7: Attach the Intake Tube to the Throttle Body

If your B5 S4 is equipped with a stock throttle body boot, inspect it for cracks. The AWE kit may include a replacement silicone hose for the throttle body if the stock boot is 20+ years old. Slide the T‑bolt clamp over the throttle body connection, then mount the other end of the AWE tube (or the included filter adapter) onto the throttle body boot. Ensure the orientation allows the MAF wiring to reach without tension. Tighten the clamp to 8 lb‑ft. Check all couplers and clamps once more – any loose connection will cause a vacuum leak, rough idle, or check engine light.

Step 8: Reinstalling the Engine Cover (Optional)

Many B5 S4 owners choose to leave the engine cover off for better heat dissipation and easier access for future work. If you wish to refit the cover, you may need to trim a small plastic tab that interferes with the AWE intake tube. Use a Dremel tool or sharp knife to remove the tab. Reinstall the cover using the original bolts, but do not overtighten (4 lb‑ft max).

Step 9: Final Checks and First Start

  • Inspect all vacuum lines and wiring – ensure no hoses were accidentally dislodged during installation.
  • Reconnect the battery – tighten the terminal clamp and set the clock.
  • Check for leaks – start the engine and let it idle for 30 seconds. Listen for hissing sounds. A slight increase in intake noise is normal, but a sharp whistle indicates a leak. Spray soapy water on all couplers and look for bubbles.
  • Monitor the check engine light – it should not illuminate. If the CEL appears, scan the code with an OBD‑II reader. Common causes: loose MAF connection, vacuum leak, or incorrect fuel trims. Resolve before driving.
  • Test drive – take the car on a short route with low to medium load. Listen for any unusual rattles (intake tube contacting the engine). Perform a few full‑throttle pulls to verify the system delivers consistent power without surging or hesitation.

Tuning and Performance Expectations

The AWE Tuning CAI alone typically adds 10–15 horsepower on a stock B5 S4 when paired with a compatible ECU tune. For maximum benefit, pair the intake with a stage 1 or stage 2 tune from a reputable tuner like APR or Unitronic. The intake will also help spool the K03 or K04 turbos more efficiently, reducing lag and improving mid‑range torque. If you plan to upgrade to larger turbos in the future, the AWE kit is compatible with most aftermarket inlets.

Common Issues and Troubleshooting

  • MAF sensor code after installation – clean the sensor with MAF cleaner (CRC or similar) and ensure the wiring harness is fully seated. Do not use oil‑based cleaners.
  • Rough idle – check for vacuum leaks at the turbo inlet hoses and throttle body boot. Also verify that the crankcase ventilation system is intact.
  • Filter rubbing against inner fender – adjust the bracket position or use a thin nylon zip tie to pull the intake tube away from the fender.
  • Heat soak after long drives – consider adding a turbo blanket and wrapping the intake tube with reflective heat tape if you live in a hot climate.

Maintenance of the AWE Cold Air Intake

AWE recommends cleaning the filter every 30,000 miles (or more frequently if you drive on dusty roads). Use the K&N cleaning kit or similar: spray the cleaner, let it soak for 10 minutes, rinse with low‑pressure water, and allow to dry completely before reapplying filter oil. Do not over‑oil the filter. Inspect the silicone couplers and clamps annually for cracks or corrosion. Re‑torque all fasteners after 500 miles to account for vibration settling.

Conclusion: Enjoy the Performance Upgrade

Installing an AWE Tuning Cold Air Intake on your B5 S4 is a straightforward afternoon project that delivers immediate and lasting improvements. With the detailed steps above and a careful approach, you can confidently upgrade your intake system and unlock the full potential of Audi’s legendary 2.7T engine. For further discussion and build ideas, the B5 S4 section on Audizine provides a wealth of community knowledge. Pair this intake with a quality tune and exhaust, and you’ll have a truly exhilarating daily driver.

For official product specifications and additional installation videos, refer to the AWE Tuning website.