From what I remember, and note, it was about 4-5 years ago.
I didnt really notice any lack of power at the time, and the knock only really happened when I was taking off from stopped.
I drive hard, but not fast (except for that one speed run, done on an unrestricted road in the Northern Territory of Australia).
Unless I'm lined up with some idiot thats got something to prove, I'm usually the first off the line at lights, but I dont gun it. I dont speed, I just get to speed quickly, then for the most part I coast.
So most noticeable at low revs, low vacuum & high excellerator input (or low revs & high load).
At the time I did that fuel mistake, I was taking it easy for the most part cos, like on most long distance trips I do, I like to check on car economy, so I tend to take it a little easier for the trip to see what I CAN get out of a tank of fuel.

Er, neither did I. I have not done anything to TUNE IT UP. Just maintained it well. It does go well thought, better than I would expected for a 33 yo vehicle.

Neither do I know of any issues, just checking before I commit. It does work out cheaper to do this for me (at least at the moment because of the massive and "unjustifiable" difference in price between RON91 and RON95 (Regular and Premium) in Australia

Thank you for your reply.