99 stalls when warm
 

Ok helping a guy with his 99 cummins it will start and run just fine for about 15min then when it warms up it's rpms start to bob up and down then stalls and isn't drivable at all stalls as soon as you put it in gear regardless of how much throttle you give it.

What we have down so farm (Autell maxisys scan tool catches no codes and no issues) Lift pump and filter new and replaced, fuel pressure coming out of the filter into the IP around 15psi and holds steady all the way threw stall. Got a remanned vp44 installed same issue tried to hotwire pump per their customer service instructions he said the bottom left pin closest to block it was red yellow stripe no change. They seem to think it's still an IP issue and are sending it to warranty claim but the exact same issue seem odd and I can't find anyone who has had this same issue exactly.

Any idea's?