GC, I can not confirm the dealer or Chevy's story, but maybe anything can be solved by the application of cubic dollars. I have no experience with this gadget, but these guys seem to think that they have the answer for you, in a box:
Your dealer is wrong. You might consider a Hypertech programmer. Pricey at $350, but it does a lot more than just recalibrate your speedometer. Look at the web sites, do a google groups search. My son put 18 inch wheels on his
99 Silverado, reprogrammed with the Hypertech and the speedo is now exact, checking it against a GPS. He's still tinkering with the shift points, but his mileage did indeed improve and he does see a performance increase based on ETs at the "race-a-cop" program at the local drag strip (Brainerd International Raceway -- Winston Nationals).Look here:
HMc
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