I think you guys missed the boat on his post. I think he's referring to exhaust cutouts used in the automobile industry. If this is the case, why do you want an exhaust cutout for a motorcycle? If you want more power, upgrade your motor and add nitrous or a turbo for added power. You'll see minimal gains, if any, using an exhaust cutout. Add these minimal gains to the added weight, and you'll probably be about where you started.