For a little extra power in your new four-door 6-series, AC Schnitzer may now be of service. For a powerboost on a 640D or 640i, you can ask this German BMW tuner. In either case, AC knows Schnitzer gets 360 horsepower from the engine to, as compared to the 313 and 320 hp diesel engine, respectively, which supply the petrol engine. You can also mount a sports exhaust, which looks better and provides a sportier sound.