I run premium in mine 100% of the time as I get better mileage. Ran BG 44K a few times through it and now switched to MOC and have no complaints, though I think I am extremely lucky buying this one.99's require premium gas.
Not so much of a problem if the prior owner used premium gas but there is a HIGH probability that they did not.
The next time it's next door I'll have the compression numbers pulled as you have me thinking. I have 213,500 miles and pulls hard and surprises me often.
I replaced the T-stat yesterday and went to back flush the core and as soon as I touched the "T" at the back of the drivers valve cover she broke! Both should be in today and I hope to get heat back at idle.
Thanks for the info.