 The Citroën C2 is an example of in-house development; the Ford Fiesta was developed by a contracted specialist (M-Sport); and the Opel Corsa was developed independently without assistance from GM.The production car's standard gearbox is replaced by a sequential manual gearbox with a maximum of six forward ratios.The engine may be modified to produce a maximum power output of 230hp and the exhaust is subject to a noise restriction of 100dB at 4500rpm.