OK, thank you to everyone who contributed (no sarcasm here). It confirms that I do understand what is going on even if my extremely simplified description of what "octane" is measuring was misleading. I had enough chemistry way back when that I could have given the entire treatment that Speedwagon present, but I just didn't feel like typing that much.
You've also confirmed that what I felt might be real and, contrary to popular belief, I might not be crazy.
Of course, the verdict is still out on that one.
So I'll try 89 from a few more sources and maybe some more 93 and see what feels best. After all, I want this beauty running her best when I take to the autocross course!