Originally Posted by RPiM5
Keep in mind that the F10 M5 still has the Primary Cat's in its downpipes, which I heard were huge (that's what she said). So even with a full exhaust system like the RPi, which eliminates the secondary cats completely, we still have the primary cats blocking a lot of the sound in the dowpipes. On the E9x M3's there are no primary cats in the headers, instead the primary cats along with the secondary cats are after the headers in the exhaust piping. So when you put a full exhaust on an M3 you can really open up the sound.
I think that I am going to pull the trigger on doing a full and complete muffler delete and that should really open up the sound before I get the catless downpipes in there.
Very interesting! Didn't know all that, and you should definitely pull the trigger!