With the new A8, Audi is set to debut the latest version of its knob-based MMI system. It’s an enhanced version of the third-generation system – “gen-three plus,” marketing head Mischa Ehlers called it – that arrived across a number of other Audis in the U.S. about a year ago. At Audi’s display in Detroit’s Cobo Center, we had a chance to check it out.