I used VP T4 this last few races in then KTM. It is a pump replacement race fuel. It runs about $13-14 gallon. I use it on all my race bikes. On our SV650's, it's 2hp pour in and a 1/2 second or more acceleration. (on dyno) You can feel the crispness of throttle when running over pump fuels. A very stable unleaded non ethanol fuel that is a 94 motor octane, 100 research method.. If I don't run this, I run 91 research method octane non ethanol pump fuel. If I don't know the local fuel quality, I run T4.
I can always go to a track around the country and know safely exactly how our bikes will perform.
Use 95 as thats what its mapped for , 98 will givr u the ability to tune more ignition advance as it resists detonation but as for performance u wont / shouldnt see any difference between 95 and 98 on standard ecu .
Placebo effect may play a part and i am / was subject to this but the physics and science supports that u won't have and advantage by just putting higher octane fuel in .
Last point is on very warm days the fuel in your tank will be warmer and inlet temps higher , this can possibly cause pre detonation of fuels in comparrison to ignition settings so if u wanted to be uber safe use 98 .
Safety margins are always good wich is why standard maps are so rich and ignition advance tame . Putting 98 in will only add a further safety margine but still not increase performance .