My integral header/catalytic converter is very rusty, so I looked into replacing it. I found BMW OEM parts for between $700 and $1200...just for that one part!
I have found some places that do aftermarket BMW parts. Try emailing this guy:
[email protected]
He sells aftermarket BMW stuff on eBay. He said he'd sell me a header for $75...which sounds suspiciously low, but he says you get your money back if you're not satisfied, and his feedback is all great.
Flunky