I'm about to go in and get some more of my new crankcase breather scrubbers made and I'm only posting here to determine interest in the units as a stand alone item.
The 928's breather system is very weak from the factory and adding any kind of boost to the engine only makes matters work. The best place to breathe from the crankcase is out of the center of the block, where the system is designed to breathe. The only problem is, on a 928 the crankcase opening sits just above the crankshaft. Any blow-by which passes the opening gets exposed to the oil which is being slung by the crankshaft. If nothing is done to eliminate the oil from this cloud, it will continue right up and out the breather port...which on the stock filler cover is waaaay too small. Here is what I do on the Twin Turbo:
Install scrubber box in the opening (trust me, no louver will better the performance of the scrubber box...been there, done that)
Port out the back side of the stock filler cover and plug the two factory ports
Drill for a 1" fitting in the oil filler cover (under the filler lid)...this requires covering the opening duting oil fill, but not that big a deal.
Install two breather ports in each valve cover
Breathe high pressure air into the non-cupped side of the valve covers
Combine the two remaining breather ports into the one inch line out of the center breather...the idea here is any blow-by in the valve train is given a path by which it can also escape with the main blow by gasses
The three outlets are T'd together and then I run them into a Provent air oil unit.
Here are a few pics of the scrubber box:
It's a prototype and I didn't have a small stainless rod that day, so production units would be better looking.
It's a 3 level approach...oil must first get past the louvers, then past a screen and finally past a copper scrubber inside the box.
I'm currently running this on my Twin Turbo and the outlet of my Provent is completely clean and dry...even after the car sits for days there is no oil on the ground (my crankcase goes out to atmosphere). The reason I use copper instead of stainless is because it is much softer.
If you are interested in one of the scrubber boxes, please let me know and I will get a batch made up on my next production run. Scrubber Box will be $100.00