6. In Europe and elsewhere, 19-inch wheels were standard, with an optional 18-inch package. In the U.S. market, the 18-inch package was the only available offering. An 18-inch winter package, with Dunlop SP Winter Sport M3 tyres () was universally available. C5 RS 6 Plus Between April 2004 and September 2004, there was a final limited run of an even higher-performance RS 6, named the Audi RS 6 Plus. This had an increased engine power output (identification code: BRV), and produced at 6,000-6,400 rpm, with the same of torque at 1,950-6,000 rpm. This engine was also developed and manufactured in the UK by Cosworth Technology (now known as MAHLE Powertrain). The additional performance was achieved with a new engine control unit (ECU), and two additional coolant radiators behind the side-mounted intercoolers (these were standard fitment on the standard RS 6 in hotter climate countries). Official performance figures indicate the discipline of sprinting from standstill to in 4.4 seconds. The RS 6 Plus carries on to reach in 20.36 seconds, and has an official top speed of . The RS 6 Plus came with Dynamic Ride Control (DRC) as standard, and also included a no-cost option of "Sports Suspension Plus", which lowered the standard sports suspension by a further over the standard RS 6. A revised steering rack, with a reduced ratio of 14.3 for firmer steering feel was included, and resulted in a turning circle of . The brakes now included cross-drilled discs. The wheels were only available in the 9Jx19-inch '5-arm design' alloys, finished in "anthracite" (dark grey), with tyres. The car was available only as an Avant and was sold only in European markets. Visual differences for the RS 6 Plus included the "black optic pack", which consisted of black finish to the framing of the radiator grille, exterior window trims, tailgate lower trim, roof rails, and exhaust tailpipes. It quickly sold out once it was released (999 units total). The last three digits of the Vehicle Identification Number (VIN) are reproduced on a plaque inside the car, displayed on the centre console. C5 RS 6 in auto racing The RS 6 was used in the North American SPEED World Challenge GT Series of auto racing for three years - 2002 to 2004, claiming the manufacturers' championship victory successively in all three years. Once again, the special race derivative of the twin-turbo V8 engine was developed and manufactured