to comply with the ROAR GT class rules, most drivers started with Offroad based engines, which where good on torque, but not that good on the topspeed side. Most competitive racers started to modify engines especially on the exhaust side, but now with the known brands either having or bringing specially designed GT class engines (OS GT, Novarossi Mito GT, WERKS GT) on the market, it is very difficult to remain competitive with an Offroad engine (without modifications) in this class.