Jeff & MBDOC,
Since I am due for servicing tomorrow, I will certainly take your advice. I'll be replacing a thermostat and then regapping the plugs.
It really was an extreme stop-gap measure to force my engine termerature higher, and although my ignition coil is new, my wires are pretty old and something would probably fail eventually if I keep it as it is.
Still, I like the car's smoother behavior, particularly at idle, and hope I do not lose it after I make the changes.