Yeah, for the record,
simi, the best octane for you to use is the lowest you can possibly get away with, without causing detonation. Using a fuel with an octane level higher than you need is actually counter-productive, and will slow you down. It's good to buy from a quality station (I'm pretty tight with Unocal), but try a tank of 89 next time, and see what happens. If it doesn't ping, try 87 the next time. If it still doesn't ping, think of all the money you're gonna save!
Take care,
~Chris