Excessive crankcase pressure due to a plugged PVC system is the first thing that comes to mind.

You might also want to post in the tech section...

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'07 Yukon 2500
'13 Subaru Outback 3.6R
'13 Orbea Carpe 9-speed

Currently Benzless
Formerly: 300TD, S600, E55, 560SEL

---= The forest breathes, listen.
-Native American elder