Tuned Pipes come in either .21 or .15/.12 size. Then the header is what fits onto the engine. There are 3 types of exaust that i know of. Rear exaust (used by high performance racing engines) standart exaust (used by most engines) and then Picco exaust which is a round-side exaust made on picco engines. The 4 tech most likely has a standard side exaust. As for a tuned pipe you can try www.rdlogics.com I got the turbo pipe for the RS4 3 and it really really made the car go faster. Gotta be doing another 3-4MPH maybe like 48 now