I HAVE SEEN SOME RYTHYM sections that weren't doable consistently without a mod motor but those are far and few between. and the motor was a factory novarossi mod motor for a nor cal pro driver. that motor was the only one with the grunt to get through it and the lap times were noticeably faster but for the average joe i would say stick with a stock motor as they are fast enough for most and get better fuel mileage.