My speedometer is like 15 miles off, and i dont have gears in it. So I was told that you can take it to the dealership and they can re-flash your computer to fix the problem, is this true?? Thanks Guys.
-John

 

Consider taking the car to a tuner shop that does dyno tuning on LS1s they can enter the rear end ratio & tire size to calibrate the speedo. PCMs can be flashed repeatedly as you add more mods you just need to have the software to do it.