on my old 4mm stock cylinder motor my rockets made 3 more hp and 3 more ft lbs of torque than cpi. the power came on sooner and turned a little more rpm. on that particular motor the rockets worked better, but on another cpi may work better. id say if you do more duning then stay away from the shearers and look more towards some cpi or the rockets. my personal nod would be to go with the rockets, but in all reality youll get a million different opinions on this...