My 1.6 Audi A3 1998 Has Been Running Very Rough I have Recently Put a Viper Catback Exhaust System On It Since Then It Has Been Running sluggish i havent yet reset the ECU as it has a few fault codes on it. The Car limits at 5000rpm, Slow Pull Away, Its Now Stalling When Starting and When Parking. It Did Have a Ram Air Induction Kit But I took it off because i was told they are not good for the car. I have changed camshaft sensor, cambelt, Air flow maf meter, spark plugs & coil pack and it still has the problem i have 2 codes still in my ecu even after trying to wipe it they are coming up as camshaft sensor and lambda sensor. i am now changing the crankshaft sensor and lambda sensor. but wondered if anyone has any idea of what else it could be??