With converters, running excessively lean will cause the catalyst to become brittle from the heat, breaking up and traveling downstream with pieces either turning sideways in the pipes and clogging your system, or if you have a chambered type muffler a broken-up piece can get trapped inside, rattling around and hindering exhaust flow.... running excessively rich will cause the catalyst to melt from contact with unburned fuel, closing the very small passages that the exhaust has to travel through, also rendereing your system ineffective...
Running water through them isn't going to accomplish anything. It would be hard for me to determine whether they are still good or not without actually seeing them, but you need to get the car properly tuned or remove the converters all together (gut them or find someone with a welder that can weld a couple pieces of tubing in where the cats were... you could also 'gut' them, but the sound of a hollow converter is a strange one.
How does one unclog catalytic converters most easily? By unbolting the rear flanges of the h-pipe, getting a long metal prybar, punch, etc. and using a hammer to beat the living hell out of the catalyst (starting the car up every few moments, reving past 3-4k rpm to clear out what has been broken up) until nothing remains inside the converter shell. I can't describe the sound of a hollow converter, but if you can accomplish the above task, you'll know what I'm talking about. ...hope this helps some
