The last piece of chrome on my 550i were the chrome Trapezoid exhaust tips. They needed to go.
I actually like the quiet ride on the 550, so replacing mufflers for sound was not an option.
After some carefull measuring I decided to install Borla Stainless Steel tips -PN 20154. (I got these from Summit Racing $55 ea)
After a trip to my local Powercoating shop - we decided on "Gray Ice" which is a Ceramic high temp - dark gray coating with a matt finish. These almost match my Ferric Grey 312 wheels perfectly. Probably would have done black if I had the M Sport black diffuser.
Cut off the old factory tips and tack welded on the new tips. Tips are slanted with a rolled lip.
Plug and wire tie off the factory vacuum line and we're done
Total cost $380