I got my '12 R55 S, Automatic, two weeks ago. It has 67000 miles, and it seems to be in superb condition. I ran Carly a couple days ago, and the only faults were several involving the DCS.

When I drove the car at the dealership, and for the first ten or so days of ownership, I noticed that it backfired frequently when decelerating, especially in Sport mode. I did my first fuel fill up yesterday, and I got 93 octane gas. Now I am not noticing the backfiring. Could that have been happening maybe because previously it had lower octane fuel?

 

The car is programed to backfire only in sport mode during deceleration. Also, the exhaust needs to be nice and hot.