Fuel question for drag ATV

Ok so Me and my brother drag race and sand drag a pair of ATV's both have 12.1:1 compression and they run on 93 but lately it seems that they r fouling plugs quicker and quicker and we have narrowed it down to the fuel, should we just run 100 octane fuel or still use the 93 from the pump but put the additive to neutralize the ethanol

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