does "what not" mean that you centered the pressure imbalance switch like you are supposed to? If not, the light will not go off. I have never done it, but there are threads that describe it. Basically, you crack one or both nuts, while a helper slightly pushes the pedal to keep air out, and the springs should center the switch, or maybe a bit more involved, so read up.
As I understand, when an adjustable proportioning valve is set properly, the fronts will lock up slightly before the rears (test in a wet parking lot). I assume the factory valve should work the same, but don't know.