A very simple and inexpensive mod is to cut the existing exhaust tips and weld on a pair of aftermarket oval exhaust tips like these two tips from Magnaflow and Ractive:






Here are some links to pix and discussion of tip installations:

http://www.xoutpost.com/x5-e53-forum/...installed.html

http://www.xoutpost.com/x5-e53-forum/...ed-w-pics.html

Expect to pay around $50 per tip + installation.