I bought year/model for 1999 Trans Am when choosing credits. but when I go to up load the new tune I'm told that I don't have enough credits. I checked the VCM to check the Vin # and serial # but the Vin # is ok but the serial # has all YYYYYYYY's. why is that? and how can I up load the new tune? The car has been tuned before I bought it and I changed some stuff and want to change the tune. Any help will be appreciated. and thanks for taking the time to look.