So I'll start by saying I've never seen anyone do what I did and I doubt many people would recommend it (I know for sure the EPA wouldn't approve).
That said, you kind of need to understand how the PCV system works to understand how oil is getting into your CAC (Charged Air Cooler = Inner cooler). Under normal non-boost operations air is pulled out of the crankcase via the PCV valve (located on the RH side or rear valve cover). This is called the dirty side of the PCV system. During this operation there is some vacuum in the intake that draws air from the crankcase that is at a higher pressure. The updated valve cover has an air/oil separator to keep the oil mist drawn into the intake manifold to a minimum. But if you are drawing dirty oil laden air out of the crankcase you have to replace it with clean air or else you get a vacuum. This is where the clean side of the PCV system comes into play. The clean side is where clean air is drawn into the crankcase to replace the dirty air that's drawn out on the dirty side. On the LH side (or front) valve cover there's a PCV hose that connects the valve cover to the air intake tubing (the plastic tubing that goes to the front turbo). So to summarize the non-boost PCV operation air passes through your air intake filter (where it filters any dust/debris), flows at atmospheric pressure through the intake plastic, flows through the clean side PCV hose, into the LH valve cover, through the crankcase, out the RH valve cover, and into the intake to be burned. As you can see, at no point is this getting into your CAC. This is how the PCV system works on any normal non-boosted vehicle and really nothing new.
Where things get interesting or different is when you reach boost. Under boost your intake manifold is under pressure and not vacuum. As a result air will not flow through the PCV valve since air doesn't travel from low crankcase pressure (usually slightly above 1 atm pressure) to high intake manifold pressure (could easily be 10+ psi above 1 atm). But under boost your car still has some blow by and causes some pressure to build inside the crankcase but it cannot exit through the dirty side of the PCV system due to that being under higher pressure. So what happens is this dirty blow-by air is forced OUT the clean side of the PCV system. This mean the air that's oil laden is pushing out the LH valve cover and back into your plastic air intake tubing. This air then mixes with clean air from the filter and flows through the turbo and into the CAC. Once in the CAC some of it will condense and fall to the bottom of the CAC where it will slowly accumulate. This is why if you remove the plastic tubing you will find a little bit of oil inside. It's due to oil laden crankcase air flowing the "wrong" direction through the clean side of the PCV system.
So what I did was very simple to keep air out of my intake tubing and out of the CAC. I disconnected the clean side PCV tubing from my plastic air intake tubing. But you cannot simply disconnect the PCV hose and let it hang because that will pull in unfiltered air under non-boost operation. So you have to get some adapters and add a filter to the end of the PCV hose (and plug the opening in the plastic air intake tubing). Once you have a filter connected it will pull clean filtered air in during non-boost operation. Then under boost operation when things flow "backwards" through the PCV clean side hose, that dirty air will flow out that filter and into the atmosphere. That dirty air is never put back into your intake air to flow through your turbo or CAC.
Sorry if that's a bit long winded but it explains what I did and why I did it.
