So my first exhaust was a pro-flo v-force muffler with custom Y-pipe which basically is the same thing as a flowmaster. I now have an aero turbine AT2525 muffler and I like it much better! Not only does it sound better and its stainless steel, but I've consistently gotten better gas mileage. Around 2 mpg better than what I had been getting. I was really suprised. But here is a video of my old exhaust and of the aero turbine.