I do need to correct myself on one detail, though. The reference for "volumetric efficiency" is atmosphere, rather than the intake manifold, as I incorrectly stated early. This does not invalidate any of the concepts or relationships I described, though. So volumetric efficiency is the percentage of a cylinder's volume worth of ambient atmosphere air (the amount of air, number of molecules, in that volume of atmosphere) that actually gets into the cylinder. Boost causes a volumetric efficiency of over 100%.