Giving me fits
 

I have a 1993 gmc short bed 4.3 v6 5 speed. I have change plugs wires cap rotor coil pack battery fuel filter. Truck runs good till it gets hot. Then it starts sputtering and looses power and runs bad. I am completly lost any suggestions would greatly appreciated. Thanks a lot.

Try the ignition control module. Both Chevy and Ford have had issues with them for years.

check your o2 sensor or sensors
i changed mine on my 94 and wow what a differance it made

Thanks appreciate it.

I changed the 02 no luck. Thinking about throttle positioning sensor and wire for my next trick.

have you looked for vacum lines leaking to do that spray some wd40 or whatever on the line around the fittings while running if it spits and sputters then the vacum line is bad do them one at a time
also check you egr valve and pcv valve and map sensor

Sounds like a typical coolant temp sensor going bad. It's the one by the thermostat.