The mainfolds SIP RACE version enables you to keep using a larger carburetor. The shorter intake beefs up your torque. Even more power can be achieved through a modification of the intake manifold membrane to reduce turbulences in the fuel flow. Shortening the intake makes a modification of the helmet compartment necessary. The fenders will have to be modified when using 28 - 30 PHB carburetors to hinder contact with the larger float chamber. We recommend a racing air filter as the original Airbox cannot b e used any more.