2001 GMC C3500 truck start to sumble, hesitates

I have a 2001 gmc 3500 crew cab utility truck with the 6.0 engine. Dual tanks . Truck started to hesitate while driving one day couldnt get out of it own way. Next day would just crank. Not fire. No fuel. Replaced fuel pump its been fine for about 15,000 miles then all of a sudden when driving again after say like 30 miles. When u mash the pedal to the floor truck starts to stumble again. Then dies. What could be the issue here. No check engine. No codes in history either. Also whats the normal fuel psi. With the vacuum to the pressure regualtor and with out