I have the Berk Race axle-back on my 2013 135i 6MT Convertible and have zero drone no matter what RPM/speed I am driving at, and other than that I just have the BMS single cone intake. I could not see replacing the stock cat back with another muffler (as the Berk Street does) and have no regrets. Actually, I wish it were louder when cruising since I can still hear my wife talking
