Everyone,

After another close call with the idle high after riding a bit today, and
realizing this time the temperature gauge had fallen below cold, I checked
the thermostat and found it was sticking. A $6 trip to the auto parts store
and 1 1/2 hours later, it's running smooth. (And the heat is much warmer
than before.)

A new thermostat did the trick!

Thanks for the help.