VW has managed to create a rather unreliable pcv system on this engine. They typically fail on chipped cars but failure is common enough on stock cars that VW has a TSB out for it.
This part replaces the VW front pcv system completely and limits the amount of oil going through the intake manifold. Why limit oil ingestion? The biggest reason is that with direct injection, no fuel washes over the intake valves to clean off any oil. Oil eventually just builds up on the intake valves and causes poor airflow and misfires. This applies to many direct injection engines. The pcv system is now routed through a catch can as well, separating fuel, oil and water vapors from the pcv tract.
Why is it good for your engine? Basically it keeps your intake valves cleaner, removes vapors that can possibly dilute the oil and prevents them from reaching the combustion chamber.
There are numerous manufacturers coming out with pcv catch can systems for the FSI engine. Eurojet has a very nice one coming out, as well as Forge. You can’t go wrong with any company, the car just needs one. I’m looking at the Eurojet one myself, their milled can just looks too sweet.
Heres the BSH Can. This is the first generation one and it no longer looks like this. It now has a metal side fitting and integrated drain valve.
They have a Stage I system which provides assurance against PCV failures and separates the intake valves from the oil vapors. However, oil vapors and what not are still flying through the pcv system. I’d still recommend the stage II if you have the cash.
Several companies now also sell a vent-to-atmosphere setup or VTA. This removes the recirculation completely, but vents out into the open air. The can has a small filter opening at the top and vapors vent out here. It can smell if you’re idling around and may leave a small area of condensation around the can. It’s not for everybody and is definitely not emissions legal. There is also a debate as to whether or not the engine performs better with vacuum drawing vapors out of the valve cover and crankcase. Personally, the smell and mess it makes in the engine bay is not worth it.
As these cans put on the miles, I can tell you that they are not the end all fix to the carbon buildup problems that direct injection engines have. They may in fact make little difference to the amount of deposits. However, they do keep oil out of the intake tract and prevent some of it from being burned in the combustion chamber. They also replace the failure prone stock pcv valve.