GMC Repair: Stumble, air intake hose, intake manifold gasket

Question
1989 GMC Jimmy
4.3 auto overdrive 4x4
Replace:
Distributor cap and rotor
Fuel filter
MAP sensor


Can drive truck for awhile then the gas peddle goes soft and the engine starts to stumble and if you don't let up on it it will stall. But will restart. If I shut the engine off and restat it the stumble goes away for awhile like I just drove about 40 miles and had it stumble three different times each time I turned off the engine and restarted it and it would run fine.

Did a fuel pressure test at idle it was 11 psi and when driving it was at 12 it would dip under heavier load but never below 10 psi.

Any suggestions as to what might be the problem?

Answer
check these for a start:

       Worn, Faulty or Damaged Carburetor.
   Fuel Filter    Clogged or Dirty Fuel Filter.
   Intake Manifold Gasket    Leaking, Worn, or Damaged Intake Manifold Gasket.
   Fresh Air Intake Hose    Clogged or Damaged FreshAir Intake Hose.
   Fuel Pump    Low Fuel Pressure.
   Fuel Injector    Dirty or Worn Fuel Injectors.