you vent your Crank Case Vapors to the atmosphere, or dump them into your exhaust.
crank case vapors have oil mist in them, when the vapors are sent back into the intake on a stock tuck, the oily mist is what makes your boots on your intercooler lines look all dirty. small leaks in the boots will leak out oily air. dirt sticks to oily parts of your tuck.
I used the Racor filter for my CCV mod with no winter problems. However it does not get 100% of the oil but it gets most of it. I am a little worried about doing the normal CCV mod because the turbo system actually creates a vacuum on the CCV. This according to some articles I have read actually increases Horse Power because of the negatice CC preasures. Not sure of course but that is why I made the choice I did. I can't imagine the Crank Case Vent freezing if you keep a downward slope.