Crankcase ventilation with blow through supercharger

What is your air filter setup? AKA piping from the filter proper to the inlet of the blower is going to generate SOME negative pressure. This will increase with throttle/ RPM. Blowby is not much at idle, so if you can put the fitting as close to the blower inlet as possible it will give you at least "some" vacuum, not much. You may have to play with valving, or use none at all, AKA open hose from rocker cover to inlet