any ideas or help is appreciated...

1997 Suburban 280,000 miles
6.5L diesel
new PMD (mounted off to side on heat sink at intake)
new fuel filter
fuel is clean (no water or debris)
drained fuel sump
battery connections are all verified good
ground connections are all verified good
not throwing any codes
lift pump working (ignition on sounds like fuel pump on a twin Beech)

At idle engine will stutter. ECU commands engine to speed up which it does and then stutters again. Repeated cycle at traffic light; stutter vroom, stutter vroom, stutter etc...

Truck had been running fine. Completed 2000 mile trip over Thanksgiving holidays and started having the trouble on way home in West Virginia. Now has gotten progressively worse where it will actually stall at idle.

First thought was a bad load of fuel. Changed filter, fuel is free of debris and water. Then changed PMD with a new one. No luck.

Funny thing. After PMD change truck seemed to run well for a couple days back and forth to work. On way home filled truck with new load of diesel from place I always purchase and problem started again. Which made me think contamination. Inspection of fuel however looks fine (opened valve and drained into glass jar).

Any ideas or guesses? Fuel injection pump finally going?

The truck runs fine at speed. Must put in neutral when coming to light. Belches black smoke as it tries to regain engine speed.
Started the truck this morning and let it idle for over 30 minutes. Started and ran just fine. As soon as I put in gear it died.
Lift pump has voltage during start and after.