This thing sounds real good but does not "get on the pipe" as with most other engines with his exhausts or other brands with Ultrathrusts etc. You know how when you open up the throttle, it only goes so hig in rpms then their is a noticable chnage in higher rpms when the pipe kicks in. This combo just goes straight up. I don't know why but the overall performance is real good. I'll let ya know after I change props