Unlike the 5.3L the 6.0L has more room for gains. Anything you install that allows the engine to work less at getting what it needs to run will increase power and mileage to some degree. Your purchases should reflect your ultimate goal. If you want mild increases do the free mods listed on this site and get a basic programmer such as a Hypertech. If you want to go crazy get a second mortgage and a beater car to drive while you work the bugs out of a radically built drivetrain.

 

I use Super chips, it was the last of my mods to date and it really made a difference. They're not the highest on the market but get the job done, I'm looking at upgrading since I'm sure there have been alot of improvements since 2004.