The regulator increases the idle above the RPM level that the AAC can reach. For all practical purposes, the air regulator is a redundant piece.
As far as regulator adjustment goes, there is not realistic way to adjust the door opening small enough to do this. I even tried a number of small air orifices in the outlet of the air regulator with very limited impact. The best thing to do is to just remove it. Your car will thank you.