I have a 2000 5.4L V8 triton and it won't start after sitting for a few hours unless I push the pedal to the floor and then it will finally sputter and idle rough til it smooths out. I tried fuel filter, replaced all the spark plugs, did a oil change, replaced thermostat, and flushed coolant. I have no idea what it could be. Fuel pump was also replaced 8 months ago. I'm stumped on what it could be maybe the fuel pressure regulator?

 

Turned out to be IAC valve