This sounds like the MAP sensor needs to be replaced. Tune up fresh? Here is a guide to help walk you through the steps and the location of the sensor for your truck below.
Lets run the codes to see if any come up. If the MAP is off a little it wont through a code..
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.