1988 Pontiac Firebird hesitate under load

This is tough one because it isn't OEM. Have you checked for vacuum leaks? What type of fuel pump are you using, the original one? As far as the dieseling, how rich is the engine running, are you using good?

New fuel pump, no vacuum leaks are evident. It's running a little on the rich side, but if I back it off much more it stalls. Could the EGR valve cause this?

Also, it's now bucking pretty good when warm and stalling when warm. Starts right back up after stall.

also, using an Edelbrock 650 four barrell carb is it possible this is not enough carb for a 350 ci motor. fuel adjusters on carb wide open, fuel pressure reg just over 1/2 open. Any more and it floods. any less and it stalls

Actually, the fuel pump is my concern. How much pressure is making its way to the carb? Also, yes a bad EGR could cause this too. Remove it and check if it for carbon build up and make sure the valve is sealing shut.