8500/8600 is debatable.. it will not work on a misshift-downshift. The engine is mechanically connected to the wheels and whatever speed the wheels are turning will force the RPM to be at a given rate based on the gearing. So if you are at 8000rpm in 3rd and shift to 2nd when you meant to go to 4th, you will force the motor to spin faster than it's redline and the ecu controlled fuel cutoff.