[vestalsin]

Could use some help with the P0420 code as well. Have a 2010 V6 108,000 miles. I got the code and just went and replaced the Cat. Reset codes, got it again, changed the downstream O2 bank 1 drivers side, reset code and just came back. Now I have a p0420, confirmed and P0300, P0301, P0305, P0306 pending. I am at a loss, as I need to pass emissions end of this week. I have changed the spark plugs few weeks ago. Only thing done to car is Doug T short headers, CAI cold air intake, MRT V2 axel back, Port n Polished Intake Manifold with a Plenum Spacer, and lastly RX Catch Can. Most of the items I have had on for a while and never popped any codes, all those items I put on I put on so I wouldn't have emissions testing issues. I want to fix the problem and not bypass it, so any ideas anyone? I thought maybe the coil packs and wires might be bad since I am getting those other codes now, if so could this cause the P0420 code as well?