Hello, I have code p0423 cat bank 1. I did a search on and found 4 possible fixes. I do now have a exhaust leak, I think its the manafold gasket, muffler shop looked at it. The coolant temp sender can cause the code also. The car did have misfires at some times, 3-6 months apart. New wires and plugs, no coil pack, strayed coil with water and no arcing or problems idling. The one item I would like to fix is the manifold gasket. I need some advice on removing the manifold, what to look for or any help to make the job go OK. I will replace the coolant sensor. The Jetta is a 02, 2.0 AZG. I really dont want replace the cat yet, big $$$. Thanks.