leaded race gas is bad for your 02's. I've run about 8 gallons of it through my 02WRX w/o problems, but not sure how long before it would create any with the o2. I have no problems with the new gas mix, car runs just as strong mileage is about the same perhaps better.

running straight 100 should give you the ability to run more boost/timing...tune it for each octane you run.