Since my car is coming out from the shop end of next week i decided on keeping it now i want to put an exhaust system but i don't know really anything about audis exhaust system what would you guys recommend for an 05 1.8t q i want to get a catback but i dont know what ads the most power and what is good. Also how much hp do you think a catback will add

Also i want to get a chip for the ecu where exactly you get that at a shop o can you have a mail in one and what will the chip add hp wise thanks

Also is ok to put a louder blow off valve on a automatic transmission i heard from a couple of guys that its not recommended