91 6cyl stalls

I have 120k miles. For the last two years my car has run well for about 30 minutes then the check engine light comes on and it cough and dies. If I let it sit for 15 or 20 minutes it starts again and runs well for another 20-30 minutes. I have changed the distributer, coil, nox senser, fuel pump, plug wires. What could it be?

If the '91 is built like my '90 these trucks have some electronics in a bad place. Between the front seats is a console - open the top and lift out the tray - do you have a silver box there? - some design wizard should not have put this bit of solid state electronics in there with out a proper way to cool it - leave the tray out and the lid open and drive it - if the odd problem goes away you may be over heating this guy - as these chips get older they may well be less heat tolerant - I installed a cooling fan in the compartment and two things - rough idle and stalling - when the beach temp was above 90f - are gone - 30k miles ago.