Your stock file is stored during the initial programming process. The stock file stays on the programmer until the device is returned to stock. Returning the car to stock will un-marry the device and allow it to be used on other vehicles. To use custom tunes on another vehicle you would need to get files made up for that which would also need a new enrollment into the Tunes for Life membership.
The process below will help you return your Mustang to stock using the BAMA X4/SF4.
1. Select “Program Vehicle” from the main menu
2. Select the “Return to Stock” option from the menu
3. Follow the device prompt to cycle the key to the ON position to setup the device for flashing and click Continue to confirm returning the vehicle back to the stock tune
4. The tuner will restore the stock tune to the PCM and count up to 100%
5. Follow device prompt(s) to cycle the key to the ON/OFF position to complete restoring the stock tune