We always unhook VSS on the race truck,actually take the whole drive out and just plug it.We,ve noticed no difference in the idleing or running of the truck(94 electrics).I do know that we run 58-6200 every week,but run over that and it shuts down the rpm,s.I don't think it shuts down the fuel it seems more like it shuts down the spark to a plug.(yes almost like shifting down a gear).I know when I miss a shift from 3rd to 4th and hit second at 5500,it will turn the tach to 9500+ and stay running on 3 cyl till I shut it off and reboot the putor.(really not recommened)