The PCV system (positive crankcase ventilation) in cars is set up to vent pressure that builds from the rotating parts in the engine. In turbo charged cars this pressure is compounded with blow by, air forced passed the piston rings. For my car, running higher then stock turbo pressure, along with a fairly high millage engine, the OEM system has a hard time keeping up. The result is oil being pushed passed seals, and into the combustion chamber leaving me with trails of blue smoke.
To solve this I beefed up some of the tubing and added my own breather with a liquid catch can.