The "system" on my engines (different brand) is a tube from the valve cover that dumps about an inch from the air filter. The idea is that he fumes get sucked into the turbo via the filter. No oil separator at all, so at high power, I also get some oil dripping out of that tube. It used to run down the side of the engine and into the bilge, so I made little catch buckets and hung them at the end of the tube. Not elegant, but it works. I don't believe there's much blow by in the engines....just a heck of a lot of suction right ahead of the turbo inlets pulling a little mist past the baffles in the valve covers. Anyway, your engine very likely has a factory crankcase ventilation system with an air/oil separator trap somewhere in the system. Most factory systems would drain the oil back to the crank case..but it might have a catch canister, as mentioned. If this system malfunctions, oil/oil mist could get to the air fliter area depending on where the suction linre is plumbed. Most of the after market offerings tap into a spacer between the turbo and the filter. You should be able to find the "plumbing" if one is installed. Then trace it back to where it enters the engine...might not be the crank case.... Bet you could find some info about the system on your engine with a little googling...the engine must have something to vent the crankcase.
Just thinking out loud...wonder how the turbo oil system is plumbed....
