i dont know what the voltages are, but if you set the multimeter to +12v, put the black on a ground point red on the pin in question it will tell you. it will read a positive or negative number. if it reads nothing, its probably the ground.
of course, you have to supply power to the unit . so putting the car in acc mode should work.
im gonna try re-sorting some of my vac hoses out to see if it helps and i might change to an oiled foam filter. otherwise, ill have to see if my stock bpv will fit with my pipes the way they are. or i guess i could track down a second blow off valve to use as a bypass.