And then you posted, in the WRONG FORUM... No BRZ's allowed in here
lol just pulling your leg.
But really you'll be fine! You were (hopefully) driving her easy as she is new. The car is factory tuned for 91, and that's how it will perform best, and make it's best power figures. On 89 you'll see poor power and poor fuel economy. Just fill up with premium min 91 and you'll be fine.