How long ago did you replace the distibutor cap and rotor?
This is the most common issue on concerns like the one you are describing.
If you installed a cheaper non OEM cap, I've seen them fail much quicker than the OEM's. The aftermarket caps have a tendancy to burn through the terminals and then crossfire to the wrong cylinder which would cause all of your symptoms.
You may also want to check the fuel pressure while it is occurring. When running, the fuel pressure should be 52psi at idle and about 64 psi when the engine is revved up. I've heard a few people that have had fuel pump issues with the temp over 80 degrees, but usually, the truck will just stall, but I suppose if the pump were just binding and not completely locking up, it could cause a lean condition which would account for your symptoms as well.
There is a bulletin from the factory about the crankshaft position sensor being the source of intermittent driveability issues as well.
Hopefully the distributor cap will fix the concern, but let me know.
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