Congrats on the Mach...forget keeping it stock, but that's just me. I do still have most of my stock junk in my parents shed out back, Dad isn't too happy about that, ha...but these cars were made to enjoy.
As far as exhaust, I have SLP LTs, matching catted X and
Magnaflow magnapack C/B, at 6000 RPMs on the highway it sounds like a fuggin freight train.