if you have a factory setup, then you have the miserable EFC (electronic feedback carb, better known as "evil F***ed up carb")
the root of your symptoms appears to be a choke that is not properly connected, thus causing air starvation. as a matter of fact, i got your exact same symptoms one day when i forgot to turn off my hand choke
after the vehicle has been running for 5 minutes or better, pull off the air cleaner, and a properly functioning choke would be facing straight up, not restricting airflow at all. yours is probably staying mostly closed off.
your choke should be controlled by a combination of a wire and a tube coming from the exhaust manifold. if either item is damaged, it wont work well, and the pipe is known for rotting out.
if thats not your problem, its somewhere in the electronics
if you plan to keep the truck for awhile and you dont have to pass emissions, i would strongly advise getting rid of the electronic carb for a normal carb. but this also requires you to replace your ignition system