Hello my 2004 z has been idling rough ever since i got the car about 4000 miles ago. The only thing that has been changed is the aem cold air intake that is on the car now. after worm up the idle drops low and sometimes the engine kocks. I just got a obd 2 reader and i noticed that 3 oxygen sensors are running at 280 milivolts and one runs at 690 milivols. When i rev the engine only the 690 one is is moving up and down. Anyone know whats going on? should i replace the sensor? thx