During my spark plug replacement, I noticed oil on a few of the plugs. One plug was noticeably burnt black. I inspected the timing cover gasket, which seems fine, but I'll verify again. There was some oil in the valley, but it was minimal and easily wiped with a rag. I plan to check the PCV system next. Any insights into these symptoms? I've heard that minor oil seepage around the intake manifold gasket is common for the 4.6 and 5.4 engines due to factory imperfections.

Here are some pictures of spark plugs, the long bolt and underneath the timing belt.

(it didn't allow my pictures to upload!)