You can get 110 locally at a dirt track, some marinas and certainly at small airstrips. My Subaru turbo has a Cobb Accessport tuning system with five settings, from no turbo boost all the way up to requiring racing gas, 110 octane. I did it once just for a hoot, and it was. Totally different beast, glad to have had AWD in it, lol.
I drive a 286 bhp 2 litre coupe and use 98 octane. Car will run fine on 95 octane. However, 98 octane makes a big difference in performance, mileage, and smoothness. Once a year I have the fuel system treated with a professional cleaning fuel - makes a helluva difference.