Stock engine, small pipe reducer where the muffler used to be (straight piped while maintaining decent back pressure) and a HUGE air filter. Sometimes youre just not lucky, it is a low cost part. Mine just idles a teensy bit too high, just enough that if the air temperature is just right the bike wont sit still in gear. But thats just because the neighbors complained about noise before i got it perfect. The back tire chirps every time i shift (im 210 lbs.) and if i wring it out i cant keep the front wheel on the ground right after shifts, so its got good strong midrange. Im switching to a better head and cam once funds are appropriate... Will keep you updated.