I'm studying the following table in Tunercat right now:
%Change to Fuel/Air Ratio VS RPM at WOT

I've noticed that there are irregular values at different RPM or temperatures.
IE: %Change to Fuel/Air Ratio VS RPM at WOT (Stock numbers)
400: 4.7
800: 4.7
1200: -.08
1600: -.08
2000: .08
2400: .08
2800: 3.1
3200: 0.0
3600: 1.6
4000: 0.8
4400: 2.3
4800: 8.6
5200: 9.8
5600: 6.6
6000: 2.7

I would normally expect a table like this to have some trend for most of it with perhaps the changes ocurring at the bottom and top of the RPM area, but it clearly varies up and down between each RPM.

Why would GM program these so differently between each RPM range?

 

The PE values are simply a final trim to get a flat line AFR throughout the entire RPM range. These values were determined empirically (through testing)and represent adjustments that GM made to get AFR right where they wanted it. They are by no means perfect for every car that comes (came) off the assembly line but they were close enough for the general public. If you change air flow characteristics of your motor (cam, headers,heads, etc) these values should be adjusted buy your tuner with the help of a WB 02.

Hope I've helped

Steve