I have read a lot of the threads about this code. I have a 2002 beetle 2.0 avh engine with 179,000 miles. This car runs perfect and idles perfect with good gas mileage. I got the code after I had the oil changed as well as the air filter. Could either of these cause the 420 code? If it ends up that I need a cat, what should I buy? The VW cats don't seem to be much good as shown by there extending warranties. A lot of people say aftermarket cats aren't good. I have a feeling VW dropped the ball with their software being to restrictive. Are there updates to the 2002 2.0 computers?