AAdams, same set up as my 2013, i bought it new last year, it was a leftover the dealer had and was to good of a deal to pass on. I have put close to 24k on it in 14 months, and would have done the tuner sooner if i would have know how much difference it made. This new package is supposed to have more power and torque than my 07 had with all the mods so i didn't think it was necessary. Man was i wrong, makes a world of difference as far as throttle response, power is very noticable.
I went with an Edge juice, color screen, no reprogramming of the stock ecm and it won't show as ever have been installed if i have to take it to the dealership for any work. It just plugs into the main harness, modifies signals and add more fuel and timing changes for power. Simple to install. Not promoteing any manufacture of tuners here, just the reason why i chose what i did. The intake uses the active air motor to, so that system stays on as well.
I kust have gotten lucky, no problems with the truck so far at all, i do change oil every 3k instead of 15k as per recomendation, cheap insurance, i use Castrol, the other major brands my oil pressure dropped 10psi so i stick with a little more expensive stuff.
Anyway, it sounds like you are getting the same mileage as i was, we bucked some winds on our last trip and did loose 2 plus mpg on a couple tanks of fuel. Once we hit Oregon and lower elevations no wind it came right back up.