I have it on my 2012 e92 and although i havent dynoed it, it certainly feels MUCH faster. really enjoy it. the diff whine may be annoying to some (and it was for the 1200 mile break in) but i am starting to really enjoy the sound.
i had a bunch of work done from Dinan and i believe their suspensions are the best, but i think diff should def be considered.
2012 E92 M3 with a bunch of Dinan stuff