I was wondering if Corsa mufflers from an e39 M5 would work for for an F10 550 application. The mufflers are offset, but if they were swapped left to right and right to left I wonder how they'd fit. As you know Corsa's are known to be drone free. I had a Corsa muffler on one of my Chevy trucks and you only heard it when you got on it or there was a load on the engine. You heard it but it was never intrusive. Corsa's sound awesome plus they are more than 1/3 of the price of a Meisterschaff (sp) or Dinan exhaus, but you'd have to get creative to install these on an F10.
If I knew this would work, this would be the route I'd go.
http://www.youtube.com/watch?v=8YKP5pDYOfg
http://corsaperf.com/product_display.aspx?product=654