Interesting idea. I don't know what our stock ECU would do. If it would let timing advance maximize (there is probably a "hard" limit that the ECU cannot exceed), that could build a bit of power, or at least keep what we have under conditions that otherwise might retard timing a bit.
I run 93 octane exclusively. Fortunately, I live close to a number of refineries and all of our premium here in every brand is 93.
I would think that if you are running 91 and can't find 93, then the octane booster would help. I'd like to know whether there is any more power to gain by going above 93. Let us know what happens if you give it a try.