Adjusting Fuel Curve

[Jon]

My EECIV SFI from a 5 liter and now running on a 3.5 liter Olds has a
MAP sensor that issues a square wave 50% duty frequency, rail to rail on
the five volt source from the ECU.  I alter the frequency, essentially
subtracting about four psi from the atmospheric pressure.  The engine
runs fine but the ECU complains that KOEO MAP is out of range.  Of
course, there's a one period delay in my digital frequency converter. 
So I wonder what happens when such a Ford is run in Denver.   TVR Jon