I know to use 12212156 OS but what is preferred form? From a 2002 Express or 2002 Camaro? A Tech2 was used to load a VIN and OS from a 2002 Express van onto my pcm but before I license it with Hptuners and calibrate it, I wanted to see what others use. Would it make more sense to use a VIN and OS from a FBody and calibrate it?