9ff is a German car tuning company based in Dortmund. It was founded by Jan Fatthauer in 2001. It specializes in converting stock Porsches into street legal racing vehicles, either as fully tuned cars,or by selling individual parts or kits.The company is best known for building one of the first cars to exceed 400 km/h, the GT9, capable of 256 mph.The former company, 9ff Fahrzeugtechnik GmbH, filed for bankruptcy in September 2013.A new company, 9ff Engineering GmbH was founded in October 2013.