My 95 suffered from this problem, but the insides of the pre-cats began crumbling and caused the main cat to become clogged. There are few sources to get pre-cats so your stuck with dealer pricing on them and there is lot of labor to replace these. A replacement main cat is available from many sources and a 'universal fit' will work fine. If the pre-cats are bad, gutting them is a lot cheaper than replacement. If the main cat is working well, you should pass an emissions test.
