Just for your information, I'm one of the people who complain about the vibration with my 2011 1LT automatic. I have used both 87 and 93 gas in Florida but the problem never solved.
Anyway, I have shipped my car to Saudi Arabia more than a year (I had like 35k+ mile on it) and start using gas 91 without ethanol. To be honest, I don't feel the vibration any more (Currently my car have 49k mile on it). I'm assuming a pure gas can help with this issue