Thanks for the suggestion Martin. I didn't find any evidence of carbon arcing. However, the metal tab on the top of the rotor that contacts the carbon was getting kind of rusty---not a surprise here in Hawaii where it seems everything rusts---and the brass part was partially discolored black on its top side and rough to the touch as if it was burned. It also was kind of a loose fit on the distributor shaft. I dug up a new rotor and it snugged down nicely when I put it in. Could a sloppy fitting rotor cause a miss?
I started the engine up and it's firing on all 6 cylinders! Since the problem was intermittent I can't declare it fixed but everything I'm doing is helping. I won't have a chance to drive it until Monday but I'll report back after I put a few miles on it.
After all the things I've had to fix---$$$---it would be nice if it was just the rotor and not a worn out distributor!
