OK - The answer is it's a gasket not an o-ring. Thank you, Ray. That means no removal without a new gasket on-hand. Stock throttle body by the way. The "sheet metal" screws into only the plastic of the intake manifold make this a higher risk endeavor than one would want.
The rest of the engine is real clean. I see this on the Taurii also. Something about the pressure drop at the throttle plate preferentially deposits crud there.
I have used the Gumout throttle-body cleaner (NOT CARBURETOR CLEANER) with success. *Your results may vary*