2.25, 2.5 or 3in downpipe?

how do you sellect the best Inch downpipe & catback systems?
are their any rule of thumbs?

With turbo bigger is better, especially if you plan to go big at some point. I have upgraded my exhuast twice, not the most economical way to do things, even if i do make my own.. Any significant ehxuast upgrade will bring about boost creep, which is another topic for another thread. The bigger the ehxuast, no cats, etc will all increase boost creep. And that WILL have to be addressed if you want to keep your motor. So if you know you'll never go for faster than high 11s, low 12s, 2.5" might make more sense. Less noise, less creep (still enough to require some work though), etc.

allright. all preatty loud though.. right.. of course their are silencers..