i am almost 100% sure that zetec just have one cat, you must have some sorta cat to be legal(it doesn't get checked where i live though), so if it's bad it's ok to replace it, you can replace it with a hi-flow cat (less than $100) but that means you must relocate cat under the engine and make sure you have a flex pipe. If you wanna replace it and it's still good, just beat the crap outta it with a hammer. I used a rubber elbow on the intake,, maybe you should switch once you get all your problems fixed. I only plan to have my intake until about april of next year, so hopefully problems won't happen with it before then.
