Received DTC code #PO430 approx. month ago-car ran horribly. Have not driven since then until this week. Now Mil light not lit but problem still present. Very rough idle upon startup with major misfire-seems to get better if I get R's up but still misfires on acceleration. Am I looking for upstream O2 sensor failure, catalytic converter problem, or could it be something w/ idle air control,MAF, throttle position sensor, etc. Any help would be greatly appreciated. Thanks!!