I had the same problem with my 89 amigo. It turned out to be the fuel filter. I had recently replaced the pump in the tank and apparently broke some rust loose. I had cleaned the tank screen and replaced the external filter when I replaced the pump.

After driving for a while (20-40 minutes) the rust would build up against the inside screen of the filter and block flow. When I turned off the key and restart the particles would drop to the bottom of the filter and I would be good for 10-20 minutes.

When I pulled the filter and tapped the inlet on the ground large pieces of rust came out. Later I had to clean the screen in the tank. The screen looked like it was plugged with dirt so I suspect bad gas.

I replaced plugs and wires and ran basic checks on the coil during t-shooting but it didn't make any difference.

Bill
89 4X4 Amigo