· Premium Member
The big improvement comes with the fuel tuning, especially in the midrange. The factories map them so lean in the mid to pass emissions, that they're barely running. As a rule, you don't gain all that much on top end power, but can see 5-6hp in the mid range. Plus you get a much smoother, better running bike all across the board once you get the A/F at 13.5:1, no matter what exhaust you have.