Larger the dp faster the spool, not that we have a problem with that though. I guaranty that if you ran open dump tubes at the end of the 3" section, you would pick up hp ESP. Up top. I'm surprised no one has run electric cut outs yet. Would be great for the track and still keep the stock cat back.
2008 335xi AT
Cobb AP stage 1, drop in filter, the rest stock
email@example.com w/ 1.86 60' (5,800' altitude)