I have a 2003 gmc it came with the 4.8 but a couple of years ago I put in a 5.3 and the computer out of the donner truck, I had to get it programed at the dealership to the VIN of the new computer for it to start and run. So now my VIN on the ecm doesnt match the VIN of the truck. Any way I want to get a mailorder tune but Im not sure how I can get my stock VIN back with out troubling the OBDII security. Also is it posible to use my hypertech to modify gear ratios after I get the mailorder tune or will it mess the tune up?

Any help is great THANKS! Bob.

 

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