You can swap back and forth- assuming you are n/a and running factory injectors. The tune will be programmed into the Doctronics, so unplugging it will not delete the tune (from the ecu). When you switch back to oem ecu, you will obviously be back on the factory ecu tuning parameters (no custom tune). After emissions, you can reinstall the doctronics and be back to where you were before. The tune is specific to the ecu, not the car. Remove ecu = remove tune. If you are thinking this route for F/I, it will not work. Oem ecu will not work with aftermarket injectors.