Capt. Geoffrey Thorpe wrote:
As a result the rate at which air is pumped out of the
intake manifold is reduced, which allows the air flow through the
throttle body to fill the manifold up to a somewhat higher pressure.

Careful.. there is very little "filling" going on. Unless you are in a
Mooney, at wide open throttle, with the ram air door open.

Manifold pressure is almost solely the effect of the engine sucking air
in by piston action past the air filter, and ram air difference is
negligible in the typical trainer.

Respectfully, you guys are trying to measure something with a micrometer
(ram air contribution), that was cut with an axe (throttle) (to quote
Jim Weir)..

I think some of the best reading on MP was in John Deakin's series of
articles on Fire Breathing Turbos. The first two I think were dedicated
to fundamentals...with and without turbo charging.

Anyone interested, go to www.avweb.com and search for his material.
Dave