Hello.
I am running my 1990 300 TT with an ECU upgrade from JWT. Should produce 378 HP but measures only about 320 HP, depending on the air temperature. Anyway the car has been running fine for 3 years now. About a year ago I have totally rebuilt my exhaust system, and after that my car makes blue smoke when the car is at low rpm (idle). The car is not de-catted, but the rear mufflers are straight-through design and the pipes are 2,5". I Think the smoke is caused by lower resistance in the system and the turbo's which are 17 years old now. The middle cat's are from Summit-racing.
Regards, Michael