Right now I'm leaning towards the fuel pump, when the truck gets warm it starts falling on its face under a load under acceleration. Full tune up, cat gutted still no change, only thing I haven't done is run a fuel pressure test. If there are any other possibilities I can look at as well. Thanks in advance.

 

New fuel filter, $10

Pressure can be OK but volume is lacking.

An Engine uses more fuel cold so I would expect low pressure or volume to be seen there first, driving cold.

If it only does it warmed up, I would think air/fuel mix issue
O2 sensors don't work until engine is warmed up, so computer runs preset air/fuel for the first 5 to 8 minutes.
EGR system also doesn't work until engine warms up.

Computer uses MAF sensor and Throttle sensor cold or warm.

Unplug the IAC valve after engine warms up, idle should drop to 500 or engine may even stall, either is good, it means no vacuum leak.