Hi just purchased a 2012 with only 23k love it so far Quick question gas cap says use 91 can not buy it here in NC Should I use 89 or 93??? Thanks

I have a new to me Eos 2009. I loved this car until I started to use regular fuel type or so i think. I started to use regular unleaded gas in my Eos 2009 two weeks ago. At this point i am an unhappy driver; it's no longer fun to drive, it drags, jerks and makes swishing noises as it has no...