:newsmile042:that will really depend on your selections, if your only putting slip-ons , a stage 1 a/c , and jet kit, it wont be as much as if you did velocity stacks and drag pipes, how much you lose is really up to you . you might want to run a bit on the lean side or vice -versa, if you really only ride in warm weather as opposed to cold you can set the carb up for that, or both and change the idle mixture screw .... really the results of sound, power, and or efficency are up to you .