Listen to the new Mustang first before buying any aftermarket exhaust. It sounds great, not loud and obnoxious. Everytime a GT gets started at work (I work at Ford dealer) I can tell its a Mustang. The factory system is 2.5 inch mandrell bent stainless steel system, it looks better than most aftermarket systems. If you want a louder car, just get new mufflers. They are right at the back of the car and can be change by anyone with a few tools, jack and jackstands. Even the exhaust manifolds look like they flow well, but I plan on replacing mine with FRRP headers. The manifolds look very easy to get to as well and the Mustang now has a single large convertor per bank. It will be interesting to see how much hp and tq one can gain with exhaust system mods, I don't think there will be much improvement over stock. The engineers at Ford looked at what Mustang owners do too their cars and incorporated many of these ideas into the new Mustangs.
