1. 97 RON doesnt cause any problems, Ive been running it for years on track, drifting, all sorts.
2. I think you misunderstood my post. The ECU will retard the ignition timing if it senses knock occurring (the sign of lower octane fuel) but I dont believe it advances the timing if it senses 101 RON, for instance, and if its not changing the timing then its unlikely theres any benefit being gained rfom running 100+ RON
From Jez @ Horsham...
"The ECU will only react to knock up to about 5.2k - if it knocks a lot in that rev and load area the ECU will switch over to the low octane maps which have around 2-3 degs less ignition advance. So you still get less advance over 5.2k if the engine is in high knock mode.
The amount of knock required to get the ECU to switch to high knock mode is still quite significant - so damage could be done before the engine switches maps. Also, pulling 2-3 degs out of the ignition map isn't really that much if you're going from 99 to 95 RON fuel.
So, I agree - run the car on 98/99 RON and if you have to run 95 then drive gently and refill with higher octane fuel asap."
hope that helps.