93 gmc siarra 2500 with an 89 350 tbi issues

[lordasshat]

I have a 93 GMC sierra 2500 with a 350 TBI that is having issues when warm.
when warm it struggles to idle it drops to about 200 rpm and stumbles and stalls. When driving runs fine so long as you don't get too far into the gas peddle. If you do lay into it it runs rough and backfires with no power.

List of parts replaced:
oil pump(old one was working but replaced it since i was replacing oil pan gasket)

oil pan gasket

distributor(whole thing Is timed correctly)

plugs & wires

ignition coil

egr valve

rebuilt throttle body

idle air

fuel filter

fuel pump and sending unit

I am having a heck of a time figuring this out and am hoping one of you have experienced a similar issue before and can point me in the right direction.

 

[lordasshat]

seems as if it was just bad gas, put in about 4 gallons and it stopped back firing also added a drying agent to the tank and its power returned. still idling really low according to the cluster and stumbling a bit but staying running.

Does any one have any thoughts on what this could be?