Originally Posted by Kev

Both the open & closed loop AFR's are lean from the factory on these motors, the O2 controller will correct the AFR in real time in the closed loop, we use the Adjustable fuel mod to correct the open loop AFR's for a lean factory mapping & for the additions of hardware like free flow filters & pipe.

Correcting the lean AFR's in the open & closed loop does not give big gains in performance but it does give the bike a much more responsive & smoother motor. We get most of our HP gains from the added hard ware with the Air box & filter system giving the biggest HP & torque gains.