Its real common for a little to leak into the intake plenum on hard cornering if you have a PCV system. You can remedy this by installing a catch can. From the sound of the condition of your motor I would say that it is likely something else, turbos or blow-by. But PCV's can cause oil buildup in the intake also. I have a very tight engine with new turbos and I have enough in my plenum from the PCV's that I can hear it bubbling when the car is hot and I turn it off. Little bit of brake cleaner can clean that up, or pulling the plenum and running it through a parts washer does wonders also. I would clean it up and see if it comes back after some EASY driving.