Abstract: An air and fuel mixing, modulating and supply means for a spark ignition internal combustion engine includes an air inlet manifold in effective connection with air and fuel metering means including a throttle. Two separate passages are provided which passages include holes in the inlet manifold. Each passage is controlled by a respective valve. Control means open or close the valves depending on engine condition. The first larger passage is effective to reduce engine vacuum when the engine speed is greater than a 1,000 rpm and the throttle is closed. The second smaller passage is effective to allow a small amount of additional air into the inlet manifold when the throttle is open and the engine speed is above 1,500 rpm.