Audi RoadJet Concept Debut in Detroit: Audi is taking the wraps off a study car by the name of Roadjet Concept at the North American International Automobile Show. A vehicle that blends the latest evolutionary stage of Audi's formal idiom with an entirely new space concept. The drive technology, too, represents a new departure: on the 300 bhp 3.2 FSI engine, innovative concepts produce an unprecedented synthesis of performance, liveliness and…