Alcohol injection is worth its weight in gold. If, however, you have to have higher octane anyway and can't find 100 unleaded (which it sounds like you can, you lucky dog), you can always use the 30% Xylene trick, but it's getting expensive. Around here a 5 gallon can of Xylene is now $43.... and it's even more in most other places... ouch. And whether you're using 100 octane from a gas pump or from your own mix of 91 and Xylene, you're burning it ALL THE TIME. Run down to Wal Mart, never exceed 35mph, and you're still burning your expensive fuel. Go with alcohol injection--it's only used when you get into boost, i.e., on demand. Also, leaded gas will eventually ruin any O2 sensor, but the Denso will give you the most mileage for the money, in my experience--and they aren't as expensive as some others. I've gotten mine on the internet at sparkplugs.com or some such name. Been a while and I've run leaded gas through it a few times, so it goes to show that they last.
Keith