I was just reading a thread in the last couple of days where this was debated. I think it may have been an older thread on e90post.
Someone who had them up both up on a lift commented that their labeling and markings on the exhaust system were different. I believe that someone said that the 335is exhaust has the flapper valve and the BMW PE doesn't. I think that it was said that the BMW PE was louder and deeper. The determination was that they're not the same. But I could be wrong.
But the 335is exhaust definitely does sound sweet! I can't wait, it's just weeks away!
Mine: 2006 Z4 Roadster (E85) | Interlagos Blue Metallic | Black Extended Nappa Leather | Carbon Leather Trim | Purchased 7/19/12
Hers: 2011 335is Coupe (E92) | Le Mans Blue Metallic | Black Dakota Leather | Dark Glacier Aluminum | 6MT | ED 5/12/11
Also Mine: (On Order) 2016 M4 (F82) | Sakhir Orange Metallic | Black Full Merino Leather | CF Trim | M DCT | Adaptive M Suspension | 19" Black Alloy Wheels | ZEC | ZLP | ZDB | ED 5/13/16