According to my Colorado emissions test it says that air/fuel adjustments, boost compensation aneroid, catalytic converter, positive crankcase ventilation, and exhaust gas recirculation are NOT APPLICABLE to my truck. The only emissions device it lists is the engine electronic controls, in which I have my Edge Module mounted right on the dash and it still passes. Mind you I turn it to 0 when I take it in for testing but they never say a thing about it. Ours is an opacity test. My truck scored 1% at 60mph, 11% at 50mph, 8% at 40mph, and 2% at zero shift which was passing. My understanding is it cannot produce more than 35% opacity for 1 second. So I am in the clear.