Why is truck keep stalling?

Does it reek of gas ? Maybe the injector(s) are stuck open or dumping fuel . I've heard flooring it eliminates the injector pulse .

I'll assume that periodically means when you go somewhere and the engine has warmed up, you stop and the engine wont restart until it has cooled a bit..... You have leaking injectors. The hot engine keeps the excess fuel atomized and when you start, and that cloud fills the cylinder and fouls plugs. When you go to full throttle, that initiates the Wide Open Throttle and turns off the negative pulse to the injectors. This is a program in the computer that's specifically meant to get you out of a flooded engine situation. Just get the injectors checked; you likely need to replace them.