Ok, I've now run into the 2nd car I'm having this issue with.

OBD1 LT1, supercharged. When the MAF sensor maxes out the injector pulsewidth stays at the same value momentarily, than quickly drops off. The PE table is having no effect after the maf sensor maxes out.

For example, injector pulsewidth will ramp up and be at around 15ms at the time the maf sensor maxes, shortly thereafter it will drop to 13/10/9 resulting in a lean condition. (all while the PE table is commanding more fuel).

I have not had this issue with OBD2 LT1's. What am I missing?

 

Never had this problem with my OBD2. I wonder if it is slipping out of PE mode for some reason. You might try adjusting the %TPS for WOT table to 0 at that RPM to see if it solves the problem. Also I would check to make sure it is staying closed loop. Sometimes when the computer detects a malfunction it goes to open loop.