2 things:
Best of luck, with whatever you choose; and:
On my 2004 mustang GT, I had Flowmaster 40s w/ cat delete. Sounded great. Mustangs are a B**ch to fix, and cost to much. I moved on, and a 2002 coupe w/ 5 spd. is fast enugh, as well as it can actually turn, "Right out of the box", so to...