some fuel system cleaners will infact clean the cat, some have reported that running Berrymans through the car for a few tanks would "refresh" the pre-cats. So some here have heard of this
and your notion is right to pass emissions you will need to correct the code.
if you don't mind the ocational rotton egg smell, and it should actually go away, get a set of mil-eliminators, it will make the pre-cat codes go away and you will be able to pass emissions
but the best overall solution would be to replace the cat in question
