Correct me if I'm wrong, but aren't the flowmaster mufflers designed to promote some back pressure since they are designed for muscle cars? I've never seen one on a turbo'd import. I'm going to look into that and report back.
Edit...
Yeah, look...
See the inside of that? For a boosted car, usually you can see right through the muffler. Although I'm sure it's fine... for the best performance you'd have been better off with something like a borla hush muffler if you want stealth or something from apex'i.
