octane

Maybe a thread for this already but what is people opinions/experience on both Petrols. I have been experimenting recently to see if you can actually notice a difference between the two, and I must say I notice it massively! The High Octane pulls better, gets me up to speed quicker, gets me...

Recently in Denmark Shell offered 99 octane for the same price as 95 (a limited time only kind of deal). My Yamaha dealer told me that the engine would ''run cleaner'' if a higher octane is used. Found some threads online but opinions seem to be divided. What do you guys think?