what kind of filter should i use to vent the stock bov?

i also noticed that air is constantly venting out of the bov followed by a huge release of pressure when letting of the gas. is it normal for the bov to always be venting air?

 

well the stock one will vent air even at idle....if you dont want it then buy a aftermarket one...U can use a little filtered that is purchase at like kragen....

 

Yes, the vacuum in the manifold is holding the valve open. It's not venting, if you look closer you should find it's actually drawing in air.

The best and cheapest filter is your existing intake.

Dave