I thought I'd just come out here and ask, as there is no way I'm going to sift through 480-some pages in the exhaust thread! Question regarding weather it's okay to use a 2.5" catback if/when going big turbo. I've yet to throw on my downpipe, and got to wondering... I'm currently using the Mountune catback, and am considering getting the CNT. But then I thought, I plan to go BT next spring. If I do, can I use a 2.5" catback or do I need to go up to a 3"? Would there be an issue doing this? And/or is it a bad idea? Any help would be appreciated.