Is a certified test and repair station doing the repairs/diagnosis on your car? Can you list exactly what has been serviced on your car ever since you owned it? Did you just tell the technician to replace your spark plugs and catalytic converter(s) or did you actually let the technician diagnose the problem?
The reason your old catalytic converters failed is because of overheating due to your excessively rich running conditions. If you don't find the culprit of why your vehicle is running rich, your catalytic converters will go bad again.
I think it might be your Mass Air Flow sensor...there's many reasons why your vehicle will run rich...so don't hold me or anyone else to this because it's actually almost impossible to tell you exactly where to look.
You definitely have a rich condition (too much fuel and not enough air).
It could be anything though....high fuel pressure, leaking fuel injectors, clogged air filter, fuel saturated oil, MAF sensor, ruptured fuel pump diaphragm, unproper routing of vacuum hoses, circuits shorting to ground, vacuum switches malfuntioning, ignition system malfunction....you get the point. You should definitely have the ignition system checked out first because of the high HC failure.
Take your car to a test AND repair station and let them do the diagnostics...they'll guaranty that your car will pass the emissions test after repairs.