too much Toluene or Xylene in your gas will ruin your fuel system's elastomers, such as seals/o-rings throughout your entire fuel delivery systems: from the o-rings and seals inside the fuel pump, fuel rails, etc. all the way to the fuel injector portion.
Don't believe me? try soaking some fuel-rail grade O-rings (mostly viton these days, not so much as neoprene) in a clear glass mason jar in Xylene or Toluene (or even Acetone) and see what happens.
Your problem with fuel should be to add techron to combat the gum/deposit formation when trying to use up the remaining old fuel in tank. Definitely mix that with fresh pump fuel and then drive/use them up as quickly as possible.
modern EFI cars have the ability to adjust to octane in gas (by using a feedback systems based on knock sensor to retard/advance the ignition timing). Don't be bothered with octane booster of some kind.
Moving forward: next time when you decide to keep fuel inside your vehicle for an extended period of time, try adding some fuel stabiliser such as red sta-bil or similar...it will keep the light, "aromatic" part of the fuel stable for an extended period of time.
Also: keeping that vehicle under the shade/in a garage with minimal temperature fluctuation would also be desirable.
Q.