For the record, I know some subie and dsm guys around here that have to run half racegas and half 93 everyday just so they do not detonate. I guess you dont need a tune for more boost/timing just expensive gas Those cars were slow as balls, so moral of the story DONT USE RACE GAS. Might foul your o2 sensor as well.

 

Leaded race gas is bad for your catalytic converter. The unleaded stuff won't hurt your cat as much as a bad rich tune will.

You have to keep in mind that different octanes of gas will burn differently adversely affecting the tune (slower for example). There is no advantage to running 100 octane unless you have deep wallets and a tune to match.