The second generation of Subaru Impreza WRX STi was introduced for the 2001 model year worldwide, but not until the 2004 model year for the U.S market. The WRX STi was a high performance version of the Subaru Impreza. In the U.S., the all wheel drive STi was fitted with a 2.5L turbocharged flat four engine, whereas in other makets, a turbocharged 2.0L unit was used. A wagon version of the STi was available outside of the U.S. for the 2001 model year, but from 2002 onward, the STi was offered exclusively as a sedan. Production of the second generation Impreza WRX STi continued until 2007, when it was replaced by the Third Generation Subaru Impreza WRX STi.