An ICE with at least one intake port and intake valve has an air inlet passage that is split by a divider wall into primary and secondary runners, the primary being smaller than the secondary. The secondary contains a flow deactivation valve for shutting off or permitting flow to the inlet port opening. The divider wall extends to a point immediately adjacent the intake valve stem so as to positively divide the passage into the two independent runners. The centerline of the primary passage is oriented so as to produce the desired swirl rate to the air flow, other geometric considerations being defined to accurately control the swirl rate of flow and velocity to provide maximum efficiency of operation; one being that the primary passage cross-sectional area be 40%-50% of the total cross-sectional area of the port opening, another being that the volume between the closed deactivation valve and the intake valve being less than 15% of the cylinder displaced volume, and including other sized ratios.