I am embarrassed to admit that when I pulled the intake, there was oil film around the ports on the intake and valley pan. The walls of the intake ports have oil on them too. I pulled the valley pan. It is oily on the back sides of the ports and the heads have a thin film of oil on them too. I'm surprised at this because I sprayed Brakleen around the ports and the RPMs didn't change at all. Maybe the oil was getting sucked up from the lifter valley, under the valley pan?
The valley pan was installed without the paper gaskets. THIS time I'll use them on both sides. I have the thin ones that come with the Fel Pro full gasket set. They are about half the thickness of the Mr Gasket ones.
Years ago, I checked the intake on the bare heads to look for a misalignment. It seemed to sit squarely to each head.

After all this, wouldn't it be wacky if it came down to a poor seal at the intake?