BMW doesn't give out too many specifics on the exhaust. I've heard there are a couple different versions. In Europe I think it just includes the rear muffler section. The version in the U.S. has two sections...the muffler, and a midpipe which deletes the resonator.
As far as the volume goes, you may just have an exhaust leak. I'd check out that possibility first as it's the easiest to fix. From what I've heard of the PE, it's a relatively quiet system compared to some options out there like a muffler delete.