M50i model features a 523-horsepower twin-turbo V8 and some desirable factory equipment, including the Parking Assistance and Climate Comfort packages, 20-inch wheels, an M Sport exhaust system, and an M Sport differential. It's also completely unmodified, and it's finished in an attractive color combination. Power comes from a 4.4-liter twin-turbocharged V8, rated at 523 horsepower and 553 lb-ft of torque. Called N63 internally, it spins the four wheels via an 8-speed automatic transmission.