increased ability to suppress detonation, preignition, pinging, etc. It allows you to run a more aggressive set up for power: more boost, and more initial timing. Race gas itself is not harmful to the O2 sensors unless it is leaded. you can also run too much octane and actually slow your car down because of the slower burn rate of that type of fuel. There are good high octane unleaded fuels available to remove the concern of doing damage to the O2 sensors or cats (if you still have them). There are varying opinions as to how high you can run stock turbos without doing damage. It's safe to say that with a good high octane fuel (say VP 103 unleaded or Sunoco 104), you can run 18 psi and an extra 3-5 degrees of initial timing and be safe. Alot of the more aggressive drag racers on the West Coast run even more boost and timing with a higher octane fuel. Hope that helps, Mark
