Bad Intake manifold gasket
 

The good news? I swapped it out in under three hours. Yep - i feel pretty proud.

The car wouldn't hold an idle and it gave CELs for cyl4 misfire and lean bank 1 codes.

Spraying carb cleaner at the gasket revealed where it was leaking. Re-torquing the intake bolts didn't help.

I do have the ThermoBloker on there and used their gaskets about 30K miles ago. sigh.

Runs good now!