[QUOTE=dd1981;12985667]Yes I did the mod before I even bolted up the exhaust. I cant say what kind of difference it made because I never had the exhaust on the car while the valve was operationa. However I can say that I did the valve mod on my stock exhaust and it made it a little deeper. Not much but you will tell a slight difference.
Here check out my DIY.
http://www.f30post.com/forums/showthread.php?t=768703[/QUOTE
I just ordered an M performance exhuast for my 335i, do you know if taking taking off the valve or flap will make it louder.
Thanks, Chris