I bought my 13 GT500 with some performance parts and an unknown tune. I've since taken it to a local performance shop and had a custom Dyno tune put onto the car. After I use my SCT X4 to take my custom tune off and revert it back to this "unknown" tune. How do I reflash it to the factory settings? I'd like to avoid taking it to Ford to avoid a high cost. I've already called several dealerships and they want at least $250. I love in the Dallas Ft. Worth area.