Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
If the outputs post cat look identical there isn't much hope you can revive them, if you want to try I would suggest 24 hour soaking in a bio clothes washing detergent then an 24 hours mild acid such as citric acid which is cheap off ebay and is also sold for descaling washing machines and dishwashers and cleaning home wine making bottles. Don't try using a pressure washer as it will destroy the matrix.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Little to be done, IMO. Plus, given the time and effort involved in getting the cats in and out, I dunno how excited I'd be about doing it twice!
Some older techs I talk to swear they've brought cats back to life by killing spark to one cylinder on each bank, getting the cats good 'n hot. Not a good idea, in my experience, but I guess you don't have much to lose! :silly: