Hi, I have a 1999 A3 1.6 8L that's failed emissions. the garage say that it's a mile out, not even close. VAG-COM has no DTS's. I've put Cataclean in the fuel and ran it for about 50 miles but the garage still days it's the same. I'm thinking of maybe changing the lambda sensor, but have no idea where it is or what tools will be required. The exhaust also chuggs out smoke when left to warm up on idle. When it hits 90 degrees is when it smokes. I'm guessing stem seals need replacing. Anybody with any tips or hints would be very much appreciated.