If you really want to send yourself into a spin go to
www.mustangexhaust.com and ask the same question. There are all kinds of cat-back systems out there and I believe most give you 5-10% power increase. I hear the flowmasters are not good for the performance increase. Bassani,Magnaflow and Borla are better.
Al, also 94 GT and soon to get magnapack mufflers
