Squeaking out of the rear pipes - yipes!

Another update. On the way home yesterday I stopped and picked up a 16 oz. Octane booster (104 w/o MMT). Then I went down to the service stations, added the whole container and then filled 'er up with 8+ US gallons of 93.

Then I drove around a few miles slowly while the whole thing mixed with the 7 gallons of 89 that were already in there.

The result? ... it's f-a-s-t! ... marginally faster than the straight 89. But still chirps and idles a bit rough. So it appears it is not the timing that is causing detonation, since I figure the octane rating is now at least 94 and it made little if any difference. I am seeing in various other posts here as well that 16 degrees init timing is about what is to be expected when total is 33-34. I had always thought that we wanted 35 total with these engines and 10 init ... gues not.

So I went back to the service station I bought the gas at - they have a good reputation for their repairs in the neighborhood - and asked one of the mechanics to have a listen. He seems to think that it's missing on one plug and running lean at the same time. I had checked 4 of the plugs in the recent past - pulled two more or less randomly from each side - and they were all fine. But he and I agreed that it's probably the last plug I'd pull that is the culprit if any are - LOL.

The engine was way to hot for me to start pulling plugs after the ride, so I will attempt to get to that in the next few days or so. I will post back then.

If anyone has anything to add, please feel free to do so.