U7191 Issues with 06 GTO - Spuddering

Hello. I've seen that others have had a similar issue but I couldn't find a resolution posted. I just purchased a predator handheld (U7191) for my 2006 Pontiac GTO. I go to tune my car with the "91 octane" performance tune and ran into issues. 1st thru 3rd gears, it seems like power is cut-off once you go above 2500-3K rpms. In 4th gear, between 2500-3500 rpm (NOT WOT or anything just cruising) It begins to spudder, almost like uncontrollable jumping. It's not a problem with the car because when I return the gto to the original setting, it runs fine (no spuddering).. What could cause this, is there something wrong with the tune/tuner possibly? Any help would be greatly appreciated. Only mods I have are a VARAM intake, shorties, and cat-back exhaust.