I have a CNC head, hand finished,on my setup with fast road cams. It is expensive but does help de-bottleneck the flowing issue. With the boltons I've got it's hard to determine the individual benefit. My rev limiter has been upped from 6750 to 7200 but would be ok to go to 8000 for short periods, however, I'm not prepared to tempt fate and dance with the devil just yet.. CNCHeads is a division of Ric Woods Engineering in Manchester. Steve