For the 2008 and up Impreza WRX STi, Subaru not only updated the chassis design, but also released a 2.5L engine with dual AVCS featured on both intake and exhaust camshafts. This engine is commonly referred to as the EJ257B platform. The STi is a series of low-volume versions with even greater power and grip were built by Subaru's in-house modifier, Subaru Tecnica International (STi). STi versions of the Impreza, which produced 280 PS (206 kW) from new, are often raced, largely unmodified, in the Group N class in various rally championships to great success. Introduced in 1994, the STi has proven to be a very popular high-performance machine in the Japanese domestic market.