2000 GMC C2500 Hard-starting after warmed up.

This truck has the 5.7 Vortec engine and it runs like a top, however once it has been started and warmed up it will not restart unless you hold the pedal to the floor while turning the key. Once it begins to start you simply let off the pedal and it assumes its normal idle just fine. It acts as if it is starved for fuel upon restarting any time after it has been cold-started. Cold-starting is no issue. Starts right up and fast idles until it warms up. Restarts are the problem. I exchanged the air-flow meter from another same truck that starts and runs fine. No change. Scanned it. No codes. Check engine light works as it should. Not indicating any issue. What are the options here? Could it be Idle control valve related? What else? Whatever it might be, where are they located? I'm "old school", restoring vehicles that don't have these computer and sensor related issues. I don't even know what to look at. Or where sometimes.

Thanks,

"too often in over my head" and off the "deep end"

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