Originally Posted by wstar

Just from switching from the stock Sport setup to 275/35 on 18s, I get a ~5-7 mph difference between GPS and the speedometer in the ~80-130-ish mph range (speedo reads high). I'm surprised UpRev hasn't offered a correction for rear end ratio and tire circumference like many programmers do on other cars. Perhaps there's some limitation in the stock ECU itself that's difficult to work around?