FARUM, Denmark — The CLK63 AMG Black Series comes from Mercedes-Benz already twice-tuned for improved performance. Still, the AMG and Black Series badges might not be enough for the most power-hungry drivers, so Denmark tuner Kleemann has taken a third shot at ramping up power in the CLK63.Kleemann fit the CLK Black Series with its 63-K2 kit that adds new exhaust manifolds, downpipes and catalytic converters to permit higher flow and alter the exhaust note. There's also a remapped ECU tuned to work with the new hardware and eke out more power from the stock 507-horsepower, 6.2-liter mill. The engine modifications are good for 38 additional hp and 32 more pound-feet of torque.The Kleemann car rides on wheels that are an inch larger than the standard CLK Black Series 19-inch rollers. The three-piece wheels are 10 inches wide up front and 11 inches wide in the rear, wrapped in 255/30 and 305/25 rubber, respectively. The only other cosmetic change is a Kleemann badge that replaces the Mercedes-Benz nameplate on the trunk lid.What this means to you: Factory-tuned cars are more potent than ever, but there's always room for just a bit more power. — Eric Tingwall, Correspondent