When my truck is cold the throttle is sticking. As soon as it warms up, it runs just fine. If I tap the gas the throttle drops. It is acting like the choke is sticking. The truck is a 92 with the 300 and is basically stock. It does have an open element air intake.

 

your truck is an efi... when its cold it has like a high idle to warm the motor up until the sensors go into a closed loop. the computer does all of this.. as the truck warms up it will gradually return to normal idle. if its something your really worried about. pull the codes see what you get..

 

Could be either the throttle itself is sticking, or the bypass solenoid is starting to get gummed up- you may want to pull the solenoid off, and spray carb clean through the ports, as well as clean the t/b with carb clean on a rag.