[christofoo]

Originally Posted by t vago

Now, (assuming that we're all in agreement about what constitutes pumping work), let's look at the strange critter known as intake manifold vacuum.

All it is, is a pressure differential between atmospheric pressure and the pressure inside the intake manifold, right? There is still an absolute pressure inside the intake manifold, right? And that pressure is still more-or-less different from the absolute pressure inside the exhaust manifold, right?

Yes.