AMG Market News: The 2012 SLK55 AMG has a naturally-aspirated version of Mercedes-Benz’s 5.5-liter V8 – dubbed the M152 engine. Therefore, no twin-turbos found in several AMGs with the M157. The new aluminum engine reports 415 horsepower and 398 pound-feet of torque as well as direct injection with a stop-start feature to help improve fuel...