[HUMMERcustoms.com/TAZ]

glennc the guy is being fairly honest with You. The programing though is not what will hurt You MPG it will be Your foot once You see the huge difference if You are running the more aggressive tuning. The different tuners come with usually 3 or 4 options from economy which will drive You nuts with all the shifting, i recommend the economy only on long travel with fairly level roads. They will usually have a stock type selection that actually has a few improvements. There will be a tow mode which My programming guy at Comp Cams recommended to run most time but, I went against that when I saw the power the perf. Mode gave. What You choose does change power and thus the lead foot factor. I ran a Comp Cams programmer that I loved and would still be running it if not for the Magnuson supercharger. Even in performance when i would keep my foot out of it most of the time and drive like a normal person I got 12.5 to 13 combined and got as high as 14.5 on the road. With supercharger I'm getting 11 mpg with self control but, I'm running 5 lb. boost tuning from superchips with no ability to lean it out and running so rich I tried a 2.75 pulley and it still runs solid rich. I think once I get My wideband tuning I will lean it out and improve the millage when I'm acting normal with My lead foot in check.
Do the exhaust Mod with a long kneck header for more low end torque, which is what the beast needs. I recommend it highly as well as air intake. I have other suggestions if You would like to PM Me. Most of these guys know what I will say as it has been discussed so no need to waste their time. But, would be glad to help further.
TAZ