Ok, if it ran well with the O2 our, that's usually a confirrmation of the cat being bad. And it was running well for an extended period after you fixed the intake hose? Unusual to take out the cat like that because these intake hoses split like clockwork on the first gens, and very few bad cats have been mentioined here.
You could eliminate the cat as mentioned above, or you could get a cat from Rockauto for around $350, and either do a DIY install, or maybe a shop would hang it on for $100 or so. But you might want to dig just a bit more about the warranty on the cat - it's a Fed, which might end-around the title issue (IDK, but probably worth another look).