I have a 2017 Titanium/AWD/2.0 turbo wit 1200miles and have been using 87 octane just fine. I recently filled up wit 91 octane premium at a top tier gas station.
WOW, big difference when I put my foot down... a lot more power
first time at dealer they cut the front rotors to remove some rust, brought it in again, second time they rebalanced all 4 tires.
I am still getting the vibration in the steering wheel...