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