I Installed this Head-pipe to the slip-on Exhaust from Dr.D I had purchased months ago! This head pipe fits well and the power was amazing over the slip on!! Much more power on the low and mid range, and it almost completely elinimated one of the biggest problems the YFZ has...Low end Throttle Bobble! My YFZ powers out of corners like never before...in Higher gears with no clutch work involved! I have not encountered any throttle bobble since the install one month ago also! Big PROPS to Dubach Racing! They have made a wonderful Product!