Abstract: A multi-stage air throttle valve assembly is provided for use in a multiple cylinder engine. The valve assembly provides a series of shiftable valve plates to provide full, maximum opening of air ports having passageways therethrough for introduction of air into the combustion cylinders of the engine. By use of two or more such sliding plates, the port size through the assembly may be maximized for enhanced volumetric entry of air into the combustion chambers. A combined reed valve assembly, fuel injectors and/or an air velocity assembly with engine are also disclosed.