Re:  MAP + MATemperature vs Mass Air Flow

The best reason I can see for using a MAF sensor is that it "sees" the valve and manifold air friction losses, which result in less air mass into the engine at higher RPM than a simple calculation using RPM, displacement and manifold  pressure. 

   For any individual engine, an RPM correction based on a one time analysis of the mass flow vs rpm on a test bench with the engine loaded would supply a correction.  I think.  Maybe not that simple?

An alternative to this form of rpm correction is to use an oxygen sensor in the exhaust to supply a correction to the fuel injected at cruising engine load. This could be done "open loop" by the pilot from a simple table that shows the best O2 level for steady load operation.  It would be equivalent to a manual mixture control, with O2 supplying  a "one variable" input for the pilot.

If the O2 sensor fails, it doesn't disable the engine.  But will reduce fuel efficiency if the pilot doesn't have other accurate information to tweak A/F ratio.

This could be one answer for simple and efficient FI.

Thomas Craig