my van turns off when I let go of the gas pedal

It happens every once in a while, I start my ram van and stays on for a couple of seconds, then I give it some gas, but when I let go of the gas pedal it turns off I had a pcm installed, but I don't know if that's the problem....please help me!!!

try idle control valve

Could be lots of things, but I'd first look at your fuel pressure.