I have a 98 GT, and I have flowmaster 40 series, that are 2 1/4 in inlet and outlet. I am probably going to order a Mac Prochamber H-Pipe 2 1/2 in. Would a muffler shop have any problem installing the H-pipe, couldn't they just use flanges? Also I was wondering if by going from 2 1/2 H-Pipe to a 2 1/4 in. Mufflers and tips, would that hurt performance or sound noticeably, or would it be way to small to not even bother getting new mufflers and tips?