Common things happen commonly. So check for the usual suspects first.
Is the wire harness connected to the Air Flow Meter? If so, peek inside the connector to be sure the metal connectors have not become displaced. Check the air ducts across the top of the engine. Splits in the accordion section are common - it can be closed while idling but open up when rev'd as the engine rocks on its mounts. Is there enough gas in the tank? If the in-tank pump is weak or not functioning it'll have problems running when the fuel level is below 1/2 full. If possible, add 5 gallons. Did you fill up just before stopping? Could that gas be contaminated? Check inside the vacuum hose that goes to the fuel pressure regulator. There should be no evidence of raw fuel in that hose. If there is the FPR has failed.
I did check to make sure the AFM was plugged in but never thought to check the pins. Worth a shot!
Did check the air tubes paying special attention to the accordian and they are good.
Should have mentioned the tank was full, and he did fill up the day before (put about 50 miles on that tank)??
Should have also mentioned that before farting around with the FPR return line, I did pull off the vacuum and no fuel. Is that the only sign of a bad FPR? Can it produce the right pressure at idle and not at higher demand?