My check engine light keeps coming on but it just switch the code it was p0430 now it gave me p0420. I replaced the cat about a year ago not even but I didn't drive it much for half the year. I have both replaced sensors 6 or 7 months ago. Just did the exhaust a week ago and I just did the spark plugs. Now I don't know what can be causing it to give me one of those codes. Does anyone have any ideas or suggestions.

Don't know if it matters its on a 00 ex all stock just headers and intake

 

You can destroy a cat pretty damn quick if the engine is running rich or is misfiring. Fix those problems before installing a new cat.