You are welcome - although @Ayune deserves credit for suggesting it first!
Valve cover bolts may just be loose, a common issue. Snug them down gently with a 10mm, clean area and re-check in a while.
Sweet. Thanks for that techstream link @Jram100 . So, when I get it, what exactly am I looking for? Are there other issues with the P0420 code that will keep me from needing catalytic converters?
Also, props to @ClassyJalopy for the idea to just snug the bolts on the VCG. A couple of the lower end on the passenger side were not even finger tight. Tightened them up on both sides, cleaned up as much of the junk as I could, and I will watch it for a while.