Well, just to update....
Turns out my CEL came back after I replaced the intake gasket. Ugh.
I finally reasoned it must not have liked the spark plugs I used. I had purchased Bosch Iridium plugs thinking it would be the last time I ever needed to do that... but the joke was on me.
I finally bought the cheapest copper plugs I could find.... Autolite Copper, and stuck them in there. Low and behold... no more CEL after a month of driving. The problem is now the idle... it's too low. Since I can't see any reason for it to idle so low, I propose it doesn't like the Autolite copper either. Other than the idle being to low, it runs great with no more CEL. I bought OEM NGK Platinum plugs... they're sitting on the bench looking at me. I'll put them in one day when they nag me enough.