With mufflers: 307 hp, 315.5 tq
Cutouts open: 316 hp, 326.5 tq
That’s 9 hp and 11 tq. I didn't think there was going to be that much difference between the two. I have 2 chamber Flowmasters, dumped. The tech guy said that Flowmaster is one of the more restrictive performance muffler. My...