FAI fuel in planes is not only for WOT flying. Many pilots in eg. Europe and Australia uses FAI, because there are often no benefits and/or need for nitro in an engine to run perfect (idle, transition, midrange, WOT) - I also know it from my own plane engines. It all depends on retune, the right plug and compression ratio. Exactly like if you start using 45% nitro instead of 25% nitro – just opposite sign. No hocus-pocus, except you will have an engine that last much longer + increased mileage.