Well don't.

I bought some octane booster Saturday morning and immediately noticed that my car felt a little slower. I decided to take it on the highway and began to notice that now the 400 would feel as it lost a little power between the shifts. Ok.. no biggie... creeping up on 85... whats this?!? Car didn't want to shift, it 'wanted' to stay at 6400 RPM. This happened again on the way to the track on the highway the next day.

In my '90 Toyota Pickup octane boosters worked great, car felt smoother, etc. But stay away from octane boosters for our V8s. They are a waste of money and something that you don't want to do before you run at the track (btw, did i mention that 6000 feet altitude KILLS performance in NA engines? ouch, I envy you lowlanders )

 

Octane boosters are made to retard combustion so it's natural that your car felt slower. If your engine isn't pinging at 91-octane, then you don't need booster, it's that simple. Your old Toyota might have felt an improvement because the booster prevented premature detonatation (common in aging vehicles) thus the power strokes were smoother, synchronized, and more efficient burning.