That addresses point #3 of my post above, Paul (I think this article was in Car & Driver - I had seen it too). What about the other three points (1, 2, and 4) - are they fallacious too, or is there some truth to them, especially in the context of 15yr+ old cars.
Some people recommend using premium fuel before an emissions check, as it gives lower HC readings. That got me thinking on the cat convertor issue for old cars - after 15 years, the cat has got to be partially plugged - wouldn't premium fuel extend its life? Again, I am just raising these issues, I do not have the answers, obviously.