From what I've read on here.... Yes, you will need to set your current "10" back to stock tune... Then, you should be able to use the SCT on 2 more VIN numbers, but they need to be switched back to the stock tunes before you switch vehicles.... From what I understand, SCT basically transfers your tune (stores the stock one on the programmer and installs a different one from the programmer) But I do not own one, I'm just goin on what I've read on here. Anyone that owns one can feel to correct me, I'm ok with that.