There is a possibility with your mileage, that the overpressure from weak rings, etc could be all it takes to make that little seal leak (plus the wear groove in the cam certainly doesn't help). You can check this out by loosening your oil cap; if it wants to "blow off" when loose, then you have a possibility here. You can check your air filter return line and your valve cover to make sure there is no blockage, if this is the case.

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