Before doing any changes. You may want to find out how the cops do measure if it is too loud or not. As it depends at what area they test it from. Is it right at the exit at muffler? At ear level standing next to it? Where they measure it from can have a big impact on reading. As they are different standards on measuring noise. db(a) is a standard that is common in North America which in short is measured at certain distance at varying degrees on a compass and averaged out.
2011 328i RWD Sports 6MT PE aFe Magnum stage 2 LUX