Sorry I didn't reply earlier... I must not have seen this thread or something. Anyway, as to how the Profec-B works -
The Balance knob is something I have yet to play with. Allegedly it makes a difference as far as how the boost comes on, hard or soft. So I don't know yet about that. As far as the other two, Lo Boost and Hi Boost, they are knobs for two different ranges of boost. Lo Boost is adjustable from 10 psi (which is what my wastegate spring is) to about 14 psi. Hi boost is adjustable from I think about 14 psi to as high as your wastegate will allow.
In that picture, Lo boost would be about 10-11 psi and Hi boost would be about 14. There's a Select button, and that's what switches the controller between Lo boost and Hi boost. Ultimately what I want to do is get that Sparco steering wheel with two buttons on it, and wire one of the buttons to that Select button. That way I can change boost levels right on the steering wheel.