This is an auto transmission tune that increases the torque limit and in some cases lowers the RPM shift points to stay in the best efficiency and torque range. Shifts are smoother and quicker. The gear number indicator is also added to the instrument cluster in most cases. Especially for large turbo setups, the clutch clamping pressure is increased to minimize slip.
This is REQUIRED if you want to run a Stage 1 or higher engine tune in in your DSG equipped vehicle.