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What is the full name for the "max MAP for idle" that you refer to?
The steady state cruising with the map below idle figure was probably driving down a hill with slight throttle to maintain speed.

IAC - Idle MAP threshold Vs Idle RPM?
Does DE occur below the value in this table? Is that what it is for?

Yep think you are correct on that one

max map for idle needs to be changed if your car has signifficantly different idle map from the base tune, so much so that it prevents the ecm from going in to idle mode when it should. Normally you would not touch it, but if your chasing why idle mode wont trigger on a conversion its something to look at. I cant remember the exact name of the field off the top of my head.

Thanks for clearing that up.
It's nice to know that I worked that out correctly.