Naw stock is the only thing you can do. There is a injection pumped that can be raised or lowered. BUT thats just to make them run correctly. If they run fine and you turn them up or down the truck will run like crap (trust me). There is a computer chip you can isntall that makes them run better. I have seen them on ebay before.
Sorry I hate to argue but unless you know what your doing and from first hand experiance DONT DO IT!!!!!!!!!!
My dad owns a auto shop and no one I know and work with could figure mine out. Some how (I haven't figured out how) when you adjust the timing you have to also adjust it electronicaly using a Tech I that the dealers have.