Power Junkie there is no such thing as a cam mod with aftermarket cams. The timing marks need be lined up with any newly installed cams. The only reason people mod the stock timing is becuse the manufacture (Yamaha).. has advanced the timing on the YFZ to de-tune the motor. The "CAM MOD" is just puting the correct timing back in place. Your basically reseting the exhaust cam to were it should be at TDC. Aftermarket cams have different lobe shape to help dirve a more aggersive valve timming. If you retard the timing more than shown in service manual your just hurting yourself.
07 YFZ 450
CT Full Exhaust
K&N Filter