I have tuned cars before in the past but I am not sure what would cause my current issue. I just recently put new tires on the truck and tuned the speedo for 265/70/16 tire. The only thing I changed was the height of the tires to 30.6 then wrote the tune back to the car. I tried to do a compare tune from the stock to the change I made and didn't see anything that would cause this. Anyone run into this issue?
99 Silverado 5.3L