any ideas what causes this? I know that blow by will do it (bad rings) but this is clean, new oil. No carbon. Could it be coming from the valve cover hose?

 

Yes, you hit it right on the dot. As the CCV oriface clogs, it causes more pressure to go to the front valve, meaning oil blown into the filter. Basic fix is to take the VC off and just clean out the orifaces and put new elbows on it.