When you say that you "start the truck and give it full throttle..." does that mean that you are starting it and instantly stabbing the pedal?
I don't care what motor you're doing that to (if you are at all
it certainly isn't a good thing to do. No/low oil pressure, cold cylinders, etc... Bad news.
If this isn't the case, well then I don't know what your problem is.
But I think the previous posters have good answers.