I read a review in the M3 forum from someone who installed the sport version, then the race, then went back to the sport.
http://www.m3post.com/forums/showthread.php?t=590965
then there's this from the E90 forum
http://www.e90post.com/forums/showthread.php?t=170812
I'd like to upgrade my exhaust but like you, I'm not sure what's the best choice. I'd like to hear the Eisenmann in person. that would really help.
__________________
2016 340i XDrive, EBII/black, 6 MT, M Sport, Track Handling, Cold Weather, Tech, Lighting, Driver Assistance Plus.
2012 Z4 35i, ED 2/24/2012, Melbourne Red Metallic, Black Leather, Carbon Trim, 6MT, M Sport, CW, PP, PS, NAV, CA.