A relatively new model, the Audi TT first dawned in 1998. It was targeted at upscale buyers looking for a premium sports coupe with solid power delivery and renowned Audi engineering. The turbocharged variant came with a 1.8L, four-cylinder-DOHC (double overhead cam) sporting a 20-valve head. Engine output was originally pegged at 150 horsepower, but quickly grew to well over 200 in later years. As with most factory turbo equipped power plants, boost levels are set on the conservative side, helping to promote reliability and longevity. However, a well-executed boost pressure increase can liberate even more power safely.
Secure one end of the boost controller to the small diameter rubber line extending from the wastegate actuator (located on the turbine housing of the turbo).
Connect the other end to the boost source outlet found on the intake side of the turbo with vacuum hose.
Zip-tie the boost controller away from hot areas (such as the turbine housing or down pipe).
Do a full-throttle run to get a baseline boost reading.
Turn the knob on the controller to raise or lower turbo boost, and test by doing a third gear pull using maximum power. This step will require several attempts to achieve desired pressure level.
A 3 to 4 psi (pounds per square inch) increase will yield substantial horsepower and torque gains, while staying within the limits of the stock fuel system. Supporting mods (such as drop-in air filter, ECU and exhaust upgrades) will further enhance power gains and minimise turbo lag. Perform all acceleration runs on a private road or track.