Thread was getting long, so decided to start another one.
Had a chance to open up the exhaust baffle housing today, and think we may have found the
problem, as predicted by many of you wise Gents.
Lower screws of the housing were "finger loose", and whitish deposit ( calcium? corrosion?) shows
at lower left of leg top. Signs of moisture heading toward lower cylinder.
Baffle itself looks perfect.
Fair amount of carbon, but have seen worse! That old SAE-30 to blame possibly?
Will clean up carbon, and install new gaskets and take it for a run.