I have about 18036 miles on my Cts and I have been getting a code of P430 so I already knew of the problem with my Catalytic converter. I haven't had it checked recently but now it seems that I may a misfire or a few misfires in the engine as the power of the engine has dramatically dropped and the check engine light blinks and then just stays on when accelerating. The engine is runs a little rough when on in park and very rough when it is in drive but on the brakes. Would all this be due to a misfire or would the culprit be the converter. I'm sure either way it goes the plugs and converter will have to be replaced.