I've had good luck with DiabloSport but can't get mine to go beyond the boot screen, it does not go into the configure mode. Just hangs.
It's an older i2, maybe get the newer DiabloSport inTune i3? I did a mid-octane canned tune on the Tahoe I used to have, now want to do the same thing to the 2013 Yukon with the 6.2L and the unneeded AFM.
Otherwise use HP tuners but it's more expensive and a real tuner. Not sure I want to tune it extensively.