Since 94 octane is very hard to find in Washington State, I was worried about using lesser fuel in the STI during the trip down to Alki Beach, Seattle. Instead of carrying a gas can in the trunk (like some of the other guys), I bought a few bottles of octane booster to try out. I know with the Cobb Accessport, I could have simply flashed the ECU with a real-time map optimized for 91 octane, but I wanted to see how smoothly the engine would run with the additive....
I'm glad to say, that it worked well and the engine ran as smoothly as ever. I have to confess though, that I did make conditions as favorable as possible: The tank was 1/2 tank full of 94 octane and I filled up with 92 octane when I added the octane booster. My main goal was to make sure the engine did not suffer and I used the Accessport to monitor the Dynamic Advance numbers.
Definition of Dynamic Advance (from Parker, Cobb Forums):
"Dynamic Advance: This is the amount of timing the ECU either adds or subtracts from the map based on how the car is running. The higher the number, the more timing the car is adding. If the car sees detonation or pinging it will pull timing out until it goes away. Positive numbers mean the ECU is getting "comfortable" with it's timing and is adding some. Usually adding timing makes more power."
So I was getting positive numbers before and after the octane booster--I'm happy :0). Now I won't have to worry so much when I travel in the US!