I think you're right but i'm not 100%. I do know that when i switched from actual mufflers to those straight-through bullets, i not only lost low-end grunt but my car now gets about 20 miles less distance per tank of gas and feels like its working harder all over the powerband. As for the noise, I don't think you're gonna get that flowmaster note much louder unless you put in a more aggressive cam....some1 correct me if im wrong on this lol.