I was teasing initially about the head gaskets on this engine. I have looked under the valve covers of hundreds of OHC engines that utilize aluminum/alloy/iron in their head construction. I have yet to come across any of them with 96k miles that did not show staining of their respective surfaces by the motor oil. The camshafts between the lobes in your picture show staining but the head surfaces only have a faint indication on the bottom in one galley. I have never seen anything like it before. Is that a Subaru thing? Just curious.