In person tune if you can. I drove 3.5 hours one way to get mine with Justin. He was great and dialed it in much better than stock. My 06 runs great, shifts great especially from 1-2, runs up to just under 6000RPM and will really take off if I am WOT running. Tow/Haul Ass mode is great. MPGs are relative depending on how much you mash the pedal. Otherwise it is just nice to drive. And considering I have the 4.8, which still pulls pretty good. Nothing compared to the 6.0.
I will get the 5.3 tuned, turn off AFM completely (currently have the Range device) as well and may get the AutoCal to have for both trucks as the cost is a bit more for the device, but relative considering I will eventually have both trucks tuned.
Really do want the Suburban to have a bit more power.....
It really is the quickest, easiest way to get some added performance out of your truck, without having to mess with a whole lot under the hood yourself.