If you increase the valve pressure (turn in the screw), you increase the valve's resistance to opening at lower vacuum levels, meaning part throttle or at idle but you also increase the occurrence of compressor surge, which is what a BOV is there to prevent in the first place.
I am ordering a set of SW20 front twin pot caliper rebuild kit for myself from the united states through my brother who is studying there in wisconsin from the local toyota dealership..another set for my friend...