Originally Posted by Asur
Get a tuner, superchips, Diablo, or Bully Dog.
Free Flow Exhaust
Those are the inexpensive mods for a some extra horses.
After that it gets more expensive
But Adding horse power is exponential, for every extra horse power you want to add to a low hp engine, the more expensive it gets as they add on.
I am not sure how much more you can achieve with those things added, but probably if you run 91+ Fuel with those you might get an extra 30hp, then if you get a specific tune made for your engine. might be more, but again, it gets more and more expensive as you go.
As stated, tuner, exhaust, CAI can't hurt. Next biggest bang for buck (albeit an expensive one) is gears; the better the mechanical advantage the easier itis for that little engine to get that big truck moving. 4.56's unless you do a helluva lot of highway driving. A converter will also help as well. You can bolt on an 08 intake, but it would be better if you were able to get your hands on a set of HO cams (or have a set ground). There is a guy on another forum who is building an Eaton boosted 4.7 (I think someone posted the picture here as well).