With Mishimoto worried about pressure differentials, it might be possible to just put check valves on both of the input lines.
Under vacuum, air should be coming in from the crankcase breather and out through the PCV.
That would be my best guess based on my [limited] knowledge. It seems most, if not all, people run 2 catch cans if they want to vent both the PCV and CCV on this platform.
I'm sure someone else with a lot more knowledge of how this all works will chime in, but that might be able to get you started. Excited to learn more about the way this system works myself. Here is a good jump-off point:
http://www.agcoauto.com/content/news/p2_articleid/197