I have an 09' and i have been running 91 (best i can find) octane since i got it about 2 months ago. 1st gear i don't feel anything but in 2nd gear if i start at a low RPMs, let say 2k and floor it. I can feel the car slowly accelerate till the turbo spools up and then from around 3.5k to red line i can feel small hesitations in the acceleration. I only feel this in 2nd gear... 1st just has to much power so all i feel is the car pulling car and i think 3rd gear doesn't really pull enough so i don't feel anything.
I though it was my imagination for awhile but i got on a smooth road and tested it out a few time and i could feel it. I figured i would try 93 octane before i make a run to the dealer... i was going to tell them about it on my 1st oil change (currently at 1.5k miles).