The first point to remember is that 87 octane is the lowest grade of pump fuel available in the US, and it is much the same as our 91 octane. The reason for that is that in the US, they have a concept they call "pump octane", which is simply the average of the fuel's Research Octane Number (RON) and its Motor Octane Number (MON). RON is determined by a chemical test, MON is determined by running the petrol in an engine, raising the compression ratio until it detonates, reading the compression ratio that happened at, and comparing it with the compression ratio at which pure octane (a common hydrocarbon) detonates. Depending on how the chemists mix the cocktail, the difference between RON and MON can be manipulated, and that is the reason the US uses the average of the two.
So, the minimum octane required for your blower is 91 RON. Using fuel of higher octane than that has no benefits, or disbenefits. If you find it a fun way to spend your money, go for it. However remember, do not use a fuel with any alcohol (either ethanol or methanol) in it if you can avoid it, since those fuels have two disadvantages for the user. First, they both attack elastomers in the fuel system, shortening the life of items like diaphragms. Second, they are both oxygenates, not pure hydrocarbons, so they must be mixed with less air to produce efficient combustion. This means you will use more of them to do the same amount of work.
