these are the part numbers:
64-31-6-958-817
64-31-6-958-818
64-31-6-958-815
64-31-6-958-816
64-31-9-159-606
51-71-8-045-623
which I got from this e90 post:
http://www.e90post.com/forums/showth...=228781&page=2
I drove it around for a week without any cowls and I could hear turbos better. Once I installed, engine noise seemed to be the same as previous.
I will see if I have anything handy to weigh the cowls. My guess would be the difference is nominal. I just like having more access to engine bay. I also thought that if I ever upgrade to CF strut braces I wouldn't want them hiding under plastic.