On the other hand, with a basic tune you can easily gain 15 wheel horsepower on your stock 4.8 or 5.3 - especially with 93 octane. What really hold these trucks back is the 3.23 or 3.42 gearing, you need to find out what you have.

This forum is tremendously helpful and supportive, but from the sounds of it you need to do a LOT more reading in your own before asking such basic questions, just saying for your own benefit. If you like, send me your tune to tune@torquesouth.com and I may have a look at what is going on

Edit: ok so it's stick and high geared, what I said applies to the AT that most have. Still, the engine can be pepped up a little - high octane fuel is your friend.