It allows excess crank case pressure to be released. Not a big deal unless you are making a lot of power or have a lot of boost "blow-by" getting past your rings.but what is it filtering? Benefits? I feel like I follow all new parts to try and learn something. I don't remember seeing that though.
this noise happens on a cold start, at about 1300rpm.
you'll hear as the video goes on and the rpms reduce as the engine gets warmer the noise disappears.