True, didn't think of that.
I found and read in the service manual for my car (actually minivan, Chrysler Grand Voyager), and googled a bit too. It is possibly a function of a lot of things, like temp, torque, throttle, RPM, acceleration rate, barometric pressure, etc. which makes it pretty much impossible to find a good indicator...
I'll try some more and see if he MAP thing is somewhat consistent in normal driving conditions, or if I have to keep guessing and hoping in every hill
