I didn't actually "find" anything to point a finger at. I got a new gasket set and cleaned up the surfaces with scotchbright till they shined then installed the gaskets. The old gaskets looked rather flat compared to the new ones but weren't cracked or broke. Right at the surface of the throttle body gasket area there was some tiny lines that- could- have been "tracks" where the leakage occured. Most likely that was the problem. Other than that I couldn't see any other areas that seemed out of place in the plenum area surface. There was no anti-freeze in the oil -thank God and now I got about 50 mi on it with no leakage. It seems the new gaskets did the trick. Thanks again, Tom