Even if you run higher octane, the stock ECU will not raise itself to run the higher octane. The ECU is designed to run 91, i.e. bad tank of gas its actually 89 instead of 91 the ECU will degrade itself to run the lower octane and never recover unless you reset your ECU. So unless you run about a tank of higher octane, racing gas, then reset your ECU, then fill up with hogh octane again then the higher octane really wont do anything.
So if you run 91 or 92 all of the time and then switch to 100 its not going to do anything but empty your mpocket faster.