I was using VP Motorsport 109 (unleaded)since i've owned a pretty much my stock car (about 5 years).
Mostly because i would get engine knock registering on my scanmaster using 91octane. Even with a TT 91 octane chip i would still get sight knock. Throwing in the race gas got rid of it.
Never had problems smogging it the last two times either and have not replaced any 02 sensors. Just regular maintainence changing plugs and oil.
In my case it performed better on race gas. Even with a stock chip and low octane chip. No knock, it will run better.
Although recently i just added an alchy kit because the cost was just too much for racing fuel that i would use just strolling around town.