Bully Dog # BY40410GMC,

In my opinion, you won't gain much power from a handheld gas tuner, sure they say it will add up to 35hp but more like 5-10 on a 5.3L in your truck, and that's probably with having to run 91 octane. The best thing you could do for a tune is get a custom tune, that way you can set it up the way you want. I know that blackbear performance is a really good GM custom tuner. They are all over the GM-truck forum that I am also apart of.

You could talk with them and they could recommend what you should do or don't do, and can set your tune up for you. That's the route I would take. Good luck.