I've got an '88 as well but with the 350 TBI- I had similar problems on a trip to Canada- we tried a different ignition module (always carry a spare) but that didn't fix it. Payed good money for an in-tank fuel pump as well- no luck there. The fuel pump is a possibility in your situation.
Mine turned out to be the ignition coil. Ran fine no-load, couldn't get out of its own way under load. BTW, the coil checked OK doing the winding check per the MM.

Is the "check engine light" coming on? If so check & see what code. I would try map sensor. Had 87 ford & had same problem. Turned out to be map sensor.

I was thinking fuel delivery problem.

Jon

Even with a good description in your post, it's really hard for even the best technician to lay his hands on the computer monitor and suddenly have the "fix" come to him as opposed to actually being there and seeing/hearing the signs & symptoms. I must agree with a few that have already mentioned it, Check Fuel Pressure! My first guess would be a fuel pump in the tank going south.

Check gasket between throttle body and intake manifold, common problem.

the four things that come to mind are plug wires, retarded timing, bent or broken push rod, or a flat cam. I have been the victim of all the above and for the valve train stuff pull the valve covers and watch for a short stroking valve while cranking.

ok, i gave up yesterday, truck is in the shop today, i'll pay the $79 to find out what's wrong with it. i did do a sensor check with a code key, it flashed 44, which signals lean exhaust, 02 sensor (2 months old)and map sensor. waterfoul i'm starting to wonder if you are right about the cat. converter, i am starting to get an exhaust leak from the manifold, last time i had one the rear converter was clogged and blew out both exhaust manifold gaskets.
thanks
sly

Ike mentioned somtething that I was thinking as well - a vacuum leak maybe the throttle body gasket, maybe something else.

Whatever you find be sure to let us know!

code 44 and stumble under load,
 

my money is on the fuel pump.you are describing a classic lean missfire condition.

ok, i talked to the mechanic today,he knows what it's doing he just doesn't know why. he said it's running lean at idle,no vaccum leaks found, he doesn't know how to check fuel pressure from the in tank fuel pump, they're rigging somethng up to test it.
at least i'm not theonly one guessing at this one. he also ruled out the fuel injectors.
seee ya
sly