Back to stock 

This feature lets you select and flash a file corresponding to the original version of the file currently installed in the vehicle.

It is available in OBD for both master and slave tools on Bosch MEDC17 and Bosch MDG1 ECUs.

If you have any doubt wether the vehicle has been already modified by another tuner or not, you can flash this file in order to bring back the car in stock mode.