While chasing misfire issues, I checked the fuel pressure to see if the pump was acting up.
When the truck is running, the gauge pressure fluctuates (flutters) between 35-50 psi.
The FSM doesn't mention this problem.
Any inputs? Thanks
Ken

I am sure the FSM mentions an expected pressure and maybe even a +/-. In any case, a 15 psi fluctuation is not good.

I followed the FSM and the static pressure is within specs, as is the leakdown and fuel flow test.

At about 35 mph, the truck will start bucking and try to lay down. backing slightly off the throttle will calm is some.
Is this a plugged fuel filter symptom?

Had a 94 ram with 318 did something similar. Wide open or barley on the throttle was fine but anything in between it would buck and run terrible. I left the lights one day and had to jump start it. Ran fine for a bit. I checked the battery and connections, turns out the battery was on its way out. Swapped in a battery and problem went away. Something to check for anyway.

i had a caravan that acted this way one time, and it was the battery as well.

Is the fuel pressure in specs when it is acting up? You need to drive it and watch the pressure.

this . Hi 990 , Fuel Pressure needs to be a STEADY 49 Pounds +or- 2 Pounds , Constant . NO dropping 15 Pounds or Fluctuations . Rig up your Fuel Pressure gauge , and go for a Drive . Watch Fuel Pressure when Magnum acts Up . The Magnum I Repaired had perfect 50PSI steady Pressure , But kept having Dying+ Laydown Issues . , Ending up being a Defective Crank Sensor , Dying on the Highway after Truck was Hot . Ronnie

Sure enough. The battery is on its way out.
It's about to turn 10 years old, so I can't complain (much) lol