STAINLESS EXHAUST HEADER, ENGINE rpm PROBLEMS?!?!

[dok47]

I bougt SPORT STAINLESS EXHAUST HEADERS (see attachment) without first taking look under hood
Now i see OEM headers have catalyst or pre-catalyst built in or i am wrong, but it looks like catalyst to me!?!?
My question is: does any one have experience with repolacing those OEM with aftermarket ones and does it efect way engine runs? Unstabe, variable RPM or any thing? Because i know people say that is not smart to remove catalyst from newer typ of engines they dont run smooth any more? But maybe it has real catalyst below car and these are just some pre catalyst...
I had them on my ex E39 and they were fine, better sound and i think it run better too, but on E39 there was no catalyst built in OEM.
What you say guys?
Thanks
here is link of STAINLESS EXHAUST HEADER to see what I am talking about:
http://cgi.ebay.com/ebaymotors/01-03-04-05-06-BMW-X5-3-0L-M54-STAINLESS-EXHAUST-HEADER_W0QQcmdZViewItemQQcategoryZ33629QQihZ006QQi temZ160274422614QQrdZ1QQsspagenameZWDVW