Diablo Tuner Not Working?

[ElwynWalsh]

About 3 months ago I put in a Diablo PredatorX in my truck to help with gear hunting at highway speeds and speedometer correction. Well. I still hunt like crazy at 65+ and my speedometer has never changed. Over the last 3 months I've tried a few different tire sizes, rev limiting settings, and even fan speeds. Nothing fixes these issues. Also I cannot accelerate past 80mph without the truck sputtering and losing power.

Now I understand that this could be because of a few mechanical issues which I don't think I've found, but I want to ensure I am not messing up this tune. This weekend im replacing spark plugs as well as it's time for it.

I have a 2016 1500 LT 4x4 4.3 v6. 6 inch pro comp with 33in Nitto Ridge Grapplers, cold air intake, stock exhaust. The tune has been set for fuel economy because when I try the 87 octane performance tune I get INSANELY hard shifts.

Any ideas?

[mikel]

lets back up...how does the truck run with the stock tune?
shifts fine/smooth?
what does it do at 65+ MPH? Will it go past 80?

What CAI is installed? It may need a custom tune for best operation.