[BArmand]

OK, another vote on the vacuum leak. and BTW, I'm not convinced it's electrical either, but it seems the symptoms point me that way. Not having a vacuum gauge, I haven't used it. Joe, if I should get one, where do I need to connect it to get an appropriate measure?

However, I checked my records because this dawned on me but I wanted to be sure. I replaced the cap, rotor and coil (that had been on the car since I got it in 2001) in April 2007. This problem first happened in June 2007 (my mother-in-law was in the passenger seat; her only time). This could likely be as little as 50 miles later, and certainly at a warmer part of what passes for a New England spring.

Bill, I checked the HEI connection. The person who installed it did indeed just jump off the existing wiring, which I now know is not good and should be addressed. I don't think this is my issue however.