I'm working on replacing the header because of a cracked catalytic converter on my '03 R53. With all of the rust, I'm struggling to get the old header out. I've already cut and drilled, but still can't get it split. Has anyone used a flange like the one below with success? If so, what size did you use. I'm having a hard time getting a part number.

 

The car needs a cat to run corectly and not throw codes! You can have the cat welded back on, or replace the whole thing with a used system, or new, if you are flush with cash!