So after running the tune for a couple tanks I can say for sure that it increased my fun AND mpg.

it was enough that the wife has mentioned getting one for the denali

and im going to do a diablew tune for that when we get the tuner for sure.
8 tanks of gas, filled at 300 miles (+ or - about 20), went like this
as bought
14.8
15.2
14.5
15.5
fixed necked down PO mistake exhaust.
16.1
16.2 (installed tune for last 100 mi of this one)
had tune in (87 octane base tune)
15.9 (driving like a 16 yr old

)
16.8 (driving like a 40 yr old)
all of the driving is a little in town and mostly the 14 mi (one way) trip to and from work on 55 mph 2 lanes.
stereo wise
I had a major set back

I think the kenwood headunit failed... ive used kenwood for my last 8 or 10 builds with no issues. but I think this one sh1t the bed. going to take the one from my burb and try it to see.