If you remove the catalyst from the system you will get a check engine light. Best suggestion is to find a decent used set, they sometimes appear on craigslist.
Cars are much more compact if you don't take them apart.
There is a theory which states that if anyone ever figures out how and why the universe came to exist it would instantly dissapear, and a less rational, more complicated one would replace it.
There is another theory which states that this has already happend...