[jon75]

Could be a bunch of different things, almost all of them sensor related. It could be a cam or crank sensor. When those go out, the computer goes into a backup mode with known good parameters that it uses to make the engine run. If the problem persists too long, it will go into limp mode, resulting in limited fuel delivery, throttle engagement and spark timing. If you had the trans with it, it wouldn't have gotten out of second gear.

I sure hope you have the diagnostic link connector hooked up in your truck somewhere....otherwise you are going to have quite a fun time testing all the sensors.