In reply to Cameron94:
In short no. If fuel is getting into your exhaust system then you will probably damage your cat, along with it generally not doing your engine any favours trying to run off 3 cylinders (and possibly setting your exhaust on fire maybe?). If you really have to drive it then unplugging that one might reduce any damage.
If it's cracked then the classic bodge up is epoxy, have a good luck at it to see if it's damaged or if there's anything obvious it could be shorting to. I'm assuming you've checked the spark plugs as well.
Post edited at 19:03