@Zeke there is no physical way this engine could produce that power safely with 98. It went lean not for lack of octane but fuel (energy) supply.
In this regard it wouldn’t matter if it were C16 or e100, leaning out fuel pressure unexpectedly at high rpm will melt stuff.
Proper practice is on 91 the knock count would cause a default to low octane and basically limp parameters if deemed the engine can’t function.
Either way is not an octane issue.
A mate has a 375KW Walkin and it pings if it's not on 98 octane, the only thing that happens is it can only take out 12 deg timing and then she will just start to ping flat out up high revs. she does not go into limp mode.
Some people will not detect that it is pinging, as it's a slight ping noise as it sounds like a little rattle that some will not pick up and some will make a real bad pinging noise.
I first came across the slight ping noise with a VL turbo that had the wick turned up and open exhaust and I said what's that noise, my wife's VS V6 stock would ping badly from new and my VS V6 that was chipped would ping but I only hear it slightly where a concrete wall was close to the car other than that I could not hear it.
My mechanic in law says new EFI cars just don't ping nowadays, BS I hear such a lot at times when just walking around town, it's like a radar to me as the head turns directly.
I have heard it with old 98 fuel in my bike with 13:1 compression, the bike had been sitting in a hot summer shed for 6 weeks, fuel tank was full but I seen a fair amount of fuel evaporated in that time and I believe 98 is more touchy to go bad.
A engine can be pinging but the ear can not pick such up and then it just progresses from there to become a louder ping.
The loudest pinging I have heard is my dads 400ci V8 run on after it was switched off, the power of that type of ping was huge, it was like bloody hell ! is it going to destroy a piston or bend a rod.