Million thanks for all the advices and suggestions.
I have read
http://www.v8sho.com/SHO/TSB0197HO2SServiceTips.htm which is a bit worrying for me as it suggests that instead of the pre-cat, it could be other things that cause P0420/0430 and would it be better off to have the mechanic to check those first(as failing emission is one thing, letting the engine deteriate and may be stalled in the middle of the road is much worse) ?
Also, out of my curiosity, if this DTC code is calculated based on the pre and post O2 sensor readings, and that the downstream O2 sensor is after the main cat, how can it know it is the pre-cat(even pinpoint which one) that is the problem ?
