What jetting are you running? I haven't had mine dyno'd, but just finished sealing up everything on my 2 inot 1 Supertrapp. I had an issue with whistling coming from the muffler, but fixed that with rtv sealant. I still have the inner pipe with the 2 cones. I just moved the cones farther back in the screen pipe and welded up the holes the adjustable plates used to attach too. It sounds real good, and I have very little decel pop, if any. When it is really hot out I get an ocassional hiccup through the carb when at cruising speed. Will probably change out the intermediate jet, from what I have reading on here.