Utilizing the already slick and solid backbone of the Impreza WRX, the WRX STI represents the zenith potential of Subaru's sport compact. STI (Subaru Tecnica International) first appeared as a limited edition, high-performance Impreza WRX in the Japanese market for 1994. The first North American version of the Subaru WRX STI would arrive for the 2004 model year as a contender against the Mitsubishi Lancer Evolution. Only available in a sedan body style, the 2004 Subaru WRX STI employed a 300-horsepower turbocharged 2.5-liter engine. A tall rear spoiler, enlarged hood scoop and special interior touches also defined the WRX STI. Returning with third generation Subaru Impreza's introduction for 2008, an updated WRX STI became a 305-horsepower, five-door hatchback. An aluminum hood, Brembo brakes and 18-inch wheels were also special equipment for the 2008 sport compact. A sedan version of the Subaru WRX STI was reinstated for 2011. Maintaining its 305-horsepower turbocharged Boxer engine, the 2015 model year brought a completely redesigned WRX STI marked with a specially-equipped 1,000-unit Launch Edition. Active Torque Vectoring was an added handling feature for the all-wheel drive performance sedan.