I recently debaffled my 2013 M800. Hv holes punched in the middle of the center plates. I won't call the center plates "mickey" as they originally had only one hole fabricated at the top. I had to take out the end plates with much efforts using a dremel to smooth out the jagged edges left after I pulled out the drilled plates.
I want to install some kind of end plates to give the pipes a neat look and add back some back pressure perhaps making the sound a little heavier.
I hv been searching the web for some possible solutions. Came across some adjustable plates meant for cars which come in a 85mm size option that just might fit snuggly inside the pipes.