Checking the basics is a good idea. Heat soak has similar symptoms, but these are not usually affected by that.
Your buddy is not off target. Check the cap and rotor. Plugged vents are common. Drill or punch them out if needed. Beware the plastic distributor housing. Clean off all thread lock and never use it. Be ready to replace the housing. Cracked housings are common too.
Think about the ignition coil. Usually they work or don't , but heat soak might be a problem there. Open the hood in the dark and look for a light show showing leakage in the system. Cheap hairspray on the whole system is a good water proofer and anti-static sealer.
Check the plugs. They are indicators for each cylinder. Clean to light gray or brown is correct. Anything else is a clue.
I think you are on track checking the fuel system. Regulator, pump, filter, injectors, check valve. All can be tested simply.
Clean the throttle body. The back side of the blade can get really bad. Clean the IAC. Idle air control valves could cause erratic idle and start issues. Clean it good and replace it if needed.
Use and ohmmeter and check the TPS. It needs to be smooth and in range.
Smell rotten eggs? Suspect a cat.
Good threads around on all these topics. Let us know what you find.
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