Well the light came back on, the dealer is going to replace the cats under the warranty.

 

In answers to other questions. the air cleaner filter is not dirty. I replaced in about 7 months ago. i could replace it again, no problem. THe car does run differently since they reprogramed. No performance change, but it does start better in the cold and doest idle as high right after a cold start. it jumps up to almost 2500RPM the instant of start and then falls to about 1500 until it warms a little then returns to normal. Before it would maintain that 2500 for a minute or two then drop all the way down to 1000. i didnt know but it didnt sound right. Apparently it was a programming issue that was solved by the Flash Update.

 

Anyways it goes in today to get the new cats.

 

Once it warms up a little (Central PA with no garage) i will look over the intake really well and check for leaks and change the filter. I may replace the front o2 sensor at that time.

Okay I guess we can close this thread soon. I got the cats replaced today. The dealer was suprisingly nice about it and was extremely quick. it took about 3 hours from the time i dropped it off until they called me to come pick it up.

 

We will see if that cures the Po420 code. If not I will be back, probably asking advice on replacing o2 sensors.