The Subaru Impreza WRX STI N13, or "VT9r"as it is known internally, was constructed by longtime Subaru Rally Team USA collaborators Vermont SportsCar specifically for the Rally America Open class. It produces approximately 303bhp from its traditional Subaru "boxer" engine and utilises a 5-speed KAPS transmission.
Eveutually the VT9r took Travis Pastrana to outright victory in the Rally America championship in 2008, and 2009. His teammate Ken Block would take 2nd and 4th respectively, before his departure for Ford. In 2010 Dave Mirra would step up to the full-bore Open class N13 to replace Block (following a season in the slower Super Production-specification STI), and following Pastrana's departure David Higgins joined Mirra for the 2011 season.
According to DiRT Rally's Chief Game Designer Paul Coleman, due to the complexities in licensing the actual R4 Impreza for DiRT Rally, they opted to reuse the model from DiRT 3 and gave it the performance specification of the R4 version.