[tsbrown]

So I installed the OEM M550i diffuser (lower bumper cover?) before my Remus axle-back exhaust is installed tomorrow with quad tips. Below is a comparison of the two diffusers with the stock 540i exhaust where you can see how much larger the opening is for the M550i exhaust.

Also a note on installation of this diffuser...it's very easy and should take no more than 15-30 minutes. You only need to remove 2 screws at the L/R outside bottom edges of the diffuser and use a trim tool to pop out the clips around the perimeter. I've seen videos where people take off the bottom piece under the car where the kick-to-open sensor is, but that is not necessary for the OEM factory M550i diffuser. It may be required for any other diffusers though, but keeping that piece installed is much easier to release the bottom edge clips.