bottom line - if you don't have $$$ to spend on an exhaust, go for it. It does throw a hidden code, but not a warning code. It doesn't create/lose any noticeable performance. I upgraded to the PE and haven't really felt the 5hp gains that it claims to add. Top speed... no. Who drives at 155mph anyway? If you do, you should be driving on the track... or the autobahn. The harmful part is still unclear. Not sure if the vacuum is there solely as a sound damping device or for something else.
'09 335i /i\ ZSP /|\ CA /i\ Piano Trim /|\ BMW PE