Hi I have a 1987 F150 V 8 302 EFI. The motor does not run right. It starts and runs fine when it is cold. Once it warms up, I have to keep it above 1000 rpm or it will die. Once I'm driving it runs really smooth. I changed out distributor cap and rotor, spark plugs and wires, ignition coil, in tank fuel pump, high pressure fuel pump, and changed the transmission fluid and filter and still no difference. Any help would be greatly appreciated. This is my only vehicle

 

It is definitely a vacuum leak. Probably around the IAC valve or the ERG. Look for loose hoses and a hissing sound.