s2konroids

Correct, to a small extent but also stop gumming up of map sensors etc over time.

surfer_crx

There is more than one train of thought with putting the catch can hose to the intake, more so on an FI car. That would be reducing the pressure in the cam cover and crank by drawing the air through the vent hoses, catch can and back to the intake. Also the higher the level of boost you run the more of a vacuum you pull on the engine. The downside being that you gum things up with oily vapours.

I wonder why people haven't started to use the vacuum pump to draw a vacuum on their catch tanks?