[MOTORHEAD]

Update:
Removed intake and found the port plug oiling problem. (se pics) As Brent said, it appears to be the intake gasket on that side. It became de-laminated and squirmed around, loosing sealing ability at the lower edge. The manifold is ported so large that there is very little sealing surface at the bottom, but why did it delaminate and squirm in the first place? Manifold may be out of square, I'll check.
Also see pic of valve stem seal. Looks ok, fits stem tighly. don't know if it's viton or not, are all viton seals blue?