Hey I have an Intune that I bought for my 2011 Sierra. Used it on the Sierra no issues, but I traded that truck in for my 2014 Silverado. The Intune will not work on this truck for some odd reason and DiabloSport isnt doing much to help me out.
DONT buy an Intune.
I'd go with what crushNchowda said and try to find a local shop with a Dyno. Especially running that lift and those tires you want the tuning to be perfect to get as much as possible out of the truck.