Since I feel all left out on the Mustang love, I'll skip right to the do-it-yourself mod section. MustangExhaust.com took a 2005 'Stang, gave it a shot on the dyno and hung a Magnaflow cat-back system underneath. The auto GT dyno'd at 250 rear-wheel horses, which equals the 300 claim from Ford when you factor the percentage lost in the tranny. The new exhaust threw in another 5 horse at the wheels. I added a Mangnaflow exhaust to my Camaro Z28 in an afternoon with only having the car up on ramps with relatively no problem. This post has a good overview of the system and some good shots of the Mustang undercarriage.