Stalling when warm

To whom this may concern,

My name is Chris and I own a 2000 Ford F-150 with the 4.6 Triton in it. Recently I have been having a really big problem with the truck. The truck runs fine when cold, but after driving for a while. Usually more than a half an hour I have a problem starting it after I turn it off, usually when it is warm and has been turned of for more than 5 minutes. When I try to start it it stalls right away.I noticed that if I keep my foot on the gas and have the rpm up(around 2000rpm) for a couple of minutes, it will idle ok and everythings fine. But it has been getting worse ! Now the problem doesn't go away unless the engine cools and if I try to drive it I have to drive it with 2 feet to keep the rpm up at a red light. It runs fine if I continue to move but when I pull up to a red light it stalls.I thought it might be the air charge temp. Sensor, but that didn't fix it. It's obvoiusly a problem only when its warm. Do you have any clue why this might be happeneing? Sorry for the long question, but I wanted to explain it as best as I could. Thank you for your time ! Mr Cogis