Something up with your ignition system...
Couple possiblities that come to mind:
First is your knock sensor. Basically, when you first start the truck, it advances the timing enough to cause the engine to start pinging, then waits for the approriate voltage signal from the knock sensor. If it doesn't get it, it switches to a fixed timing table, and sets an error code. Check to see if you've got any resistance in your knock sensor, if its an open connection, something is wrong. You won't get a continuity test to work, need to actually check the ohms. I think TBI sensors are suppost to be either 100k ohms, or 3.8k ohms...
Second is a bad ignition module. Try taking it to your local parts house, many of them can test them for you.
Third is a bad EST module. Its the big flat module just to the pass side of your throttle body. I've never personally had one go bad, but I imagine is a possiblity.
