Originally Posted by ///Metak
I figured it was for the diff. because it right by those particular bends, but how much of an issue is heat going to be with the aftermarket systems? I'm not losing sleep or anything, just curious.
OE exhaust applications typically go overboard on such things like heat shielding to avoid unintended consequences. (even if the chances of any real impact are remote)
The engineering group at Arvin Meritor, (M3 OE exhaust supplier) probably suggested this to BMW during their R&D.
This precaution was implemented due to the close proximity of the dual exhaust pipes as they 'snake' around the differential casing.
I can't see that it would make much difference, but I guess it wouldn't hurt to re-use them. (or fabricate something similar)
I would only do this if you are truly concerned about the additional heat transfer from your unshielded aftermarket exhaust.
No idea how much difference it really makes...