Here is a compare on a dragstrip with corrected values to weather and where to sealevel

Both C6s have headers and PCM tuned.

1 C6 - shows stock ET and trap speeds when stock, then after a vendor installed headers and a DYNO tune and then vendor re-tuning again

2nd C6 is teammate Brett's with headers but Team ZR-1 tuned. We never saw the car, tune was all done via emails using Ease OBD scanner for recording, analyzed the data and then we emailing a custom tune to Brett.

End result Brett's C6 is 1/2 second and 5 MPH faster.
Again shows the tune method will make or break you

I can imagine you won't explain in detail what you made, but it would be interesting to roughly know which program areas you touched.

I can image IFR, PE and timing... I just can't belive this is enough to gain 1/2 second!

Your assuming the quicker C6 is all due to the tune but your forgetting the bad tune could have made the other C6 even slower.

The good tune clearly made gains from a true custom tune that touches all functions of the PCM and assures powertrain performs well from startup through PE to WOT.
I do NOT just tune for WOT and as you know its as important for engine to perform well to get to WOT as those who are just tuning for WOT.

So yes I touch everything that I can when tuning but again it is the OBD scanner recorded data I spend as much time analyzing as time to do the tune as that data tells us exactly what engine needs to perform at it's best.

Clearly the shop that tuned the other C6 knows nothing about tuning and I'd bet they do not even use a OBD scanner and custom tune to that car and the driving habits of the owner.

...tuning without scanning...
I remember my surprise as I looked into the Hypertech program and its results. Such a mess!
They changed MAF calibration, timing, PE and a couple of other things.
Fuel trims were allover the place, a lot of knock and way too lean. COT was still enable so it was randomly reach/lean at WOT.