My X5 M50d diesel exhaust has dual pipes into the rear muffler the same as the V8 has. I believe your diesel only has one pipe.
I have a reasonable exhaust note and a slight rumble in the cabin from the larger diameter exhaust. And the tune also has a lot to do with the exhaust note also, we also don't have all that addon emissions hardware either.
X5 F15 M50d White, 20"rims, Yellow Calipers, Ceramic Pads. Better off saying what it does not have and that's a B&O Audio System, otherwise all option boxes are ticked.