I have the same issue.. Cat 2 has split just at its rear seam..
The original exhaust has centre and rear sections in one piece..
Replacements come in 2 sections..
BMW are happy to cut the old one and fit a new centre section.. for £478.50 *ouch*
National will fit both sections for £450
dilema.. is it worth going for the BMW exhaust.. bearing in mind i've done 60k in 5yrs on the original exhaust its lasted ages..
Also whats the deal with just swapping for a full stainless?
any advice/experiences/links to cheaper parts appreciated..