One more time - Back to the subject at hand:
I know that MAP is measured on an aneroid device - in other words a barometer that measures absolute pressure. It happens to be calibrated just like a US barometer, in inches of mercury. Which means it will (when shut down) vary from day to day, just like a mercury barometer as weather patterns change.
It will similarly read low at a high-altitude airfield, e.g about 24" at 5000', vs nominally 29.92" at sea level.
But the BOOST gage - am I correct in perceiving it as a "PSIG" instrument, as opposed to an absolute pressure device? If so, with the engine shut down, it will read zero boost REGARDLESS OF ALTITUDE or weather patterns.
Am I correct here, or is the boost gauge also an aneroid device? As I re-read Lightning Mate, I believe he and I agree that boost is a "PSIG" parameter.