Originally Posted by HeelToe
I had an Eisenmann on my e90 330i for 2 years and then replaced with the BMW Perf exhaust because I couldn't stand the drone when cruising. Obviously this comment doesn't apply to an n55 135. I can say though that my 135is with the BMW perf exhaust is unbelievable.
Im considering the BMW performance exhaust, I haven't heard any sound clips or hp gain numbers, did you notice a big difference, BMW website doesn't say too much and 1250 is a reasonable cost