My Dad's M6 has the cam gear, and passes smog easily. The car has a Dinan chip also. From my own experience, the cam gear is not worth the time or money. The Dinan chip made a huge difference. The cam gear gave it a bit more torque down low, but I feel the car's topend power suffered dramatically. I know it says a loss of 2hp at the top end, but the delivery of power is what makes these cars fun. I personally like the way the car felt before the camgear....it pulled hard all the way to 6500rpm.