Bob,
To answer some of your questions:
I developed the 2" based on experimentation at various altitudes and temperatures, and measuring actual fuel consumption (with a dip stick). So cockpit instrumentation is irrelevant.
I fly from 13 - 20,000 feet most of the time, I didn't experiment at the lower altitudes. For 13 - 20K, OAT from -35 to +20 C, I did not detect a signifcant difference in fuel consumption. I suspect there was one, but I think the difference is buried in the basic inaccuracy of my measurements, i.e. +/- 1 gallon per tank.
My MP gauges may be both out the same amount in the same direction, but I doubt it. One guage does seem to be about 1/2" off based on indication at sea level. But again, I don't care what the indication is, I just want to run my engines at 63-67% power.
TCM manual is at the hangar.
50 ROP is of course not the same horsepower as peak, and you know that, this must be one of your stalking horse questions.
Rear tach IS out by 50 RPM, checked using ground instrument. If either tach or MP gauge goes out of adjustment, I will detect the difference in unusual fuel flow, low or high, and investigate.
I agree, an interesting discussion
Kevin