When the tunes are loaded into it, the tuner can leave adjustability turned on or off. If they leave it turned on, the owner can then make some adjustments as they go, some of the adjustments are boost, spark and WOT fuel, these are just some basic adjustments, not like the proper tuning stuff but enough for owners to have a play. But I would suspect that a tuner would not leave adjustability turned on,on a tune that is allready customised as the owner could make it go bad pretty quickly. Another option would be the tuner only allow adjustability one way, for example add fuel but not remove it, or pull timing rather than add it. The unit can aslo check and clear some OBD2 codes And with this unit and the free software from SCT you can data log your car, like a tuner can. Tune wise, there is no benefit because the same result can be acheived with either unit. Also the tunes are actually shown on the screen, so no trying to remember which tune is in which slot.