EJ257 / EJ255 CAMSHAFTS 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. Introduced to the United States in 2004, the US model STi features the larger displacement 2.5L (EJ257) that features AVCS. These camshafts will also fit the 2006-2007 GDF/GDB/GDG WRX and STi Impreza (also known as the V9 or “Hawk Eye”) in the UK.