Not cranking over when hot

Let me start by saying it's a motor swap and I don't know the actual mileage, but I have a brand new battery, alternator was fine when I disconnected the battery while running, voltmeter says all those numbers are good. I put in a brand new AC/Delco pro ignition coil, brand new plugs and wires, map sensor, IAC, ECT, radiator, thermostat, breather, tbi injectors, trans lines, oil cooler, all that is brand new. So just about everything under the hood is new, lol. When I start the truck after it's been sitting for awhile, it fires right up with no problem. If I warm up the engine and shut it off, I go to start it right back up and it acts like it's barely getting any power and will barely turn the starter over and the dash lights are severely dimmed. Is this a symptom of the ignition control module? Because it will start surging and drop the rpm's low enough that it actually died on me pulling into my driveway once. I've also been told the fuel line could be vapor locked, and I know absolutely nothing about that department. I knew nothing about car repair until I bought this truck back in January, but I have figured out a heck of a lot from YouTube and with the Haynes manual, and mainly by just diving right into it. I can't work on any other vehicles, but I darn sure know this truck, lol.