Looking to buy this 2014 mustang GT with a VMP supercharger on it. Found it for a great price. Car drives great but when coasting to a stop in neutral, engine shits off. Only happens when I'm driving, put it in neutral, and then the rpm just drop until the engine shits off. Car has the supercharger, catless mid pipe, and that's really it. I don't know why tunes the car. Any ideas?