as mentioned above, there have been several car mag tests on octane boosters and most won't raise it enough to make it worth your money. remember that if it says it'll raise it by 5 points, it's not 87 up to 92, it's 87 to 87.5 and that's a maybe.
just don't run the engine wot and take it a little easier on it. the computer and sensors will do the rest.