[olddog]

This is my gut feeling. I only know about half as much as I need to know to be of much help.

If the map sensor calibration is skewed at the lower pressure range, and someone has tuned it to work, the tables might look strange.

As I understand it, when the key is first turned on the MAP reading is saved before the engine is cranked. This lets the ECU know what the atmospheric pressure is. Even though you could tune an engine to run correctly with a skewed MAP, that tuning would only be good at that elevation. When you moved to radically different elevation, I think the tune would fall apart.