I'm trying to figure out I have a rev9 cat back exhaust on my Mark 6 and I want to put a down pipe on it and now my Rev 9 is 2.5 what size down pipe what I need to connect them and what is a good downpipe to mix with the Rev 9 exhaust and also good for when I want to tuner to stage 1 or stage 2...
Im new to messing with the ecu. What is the best way to get it tuned. I have a CTS turbo intake and rev 9 exhaust no down pipe would it hurt not to have a down pipe or intercooler for the tune