[bmw13]

I noticed that the stock 1M exhaust gets extra loud all of a sudden around 2200-2300 RPM. I recall this happening on all N54's and there being a exhaust flap/ valve in which opens around that RPM range. As I did the golf tee mod on my last car I quickly found myself under the car looking... and I found nothing similar to that system. Are all four open? If all four really are open, there has to be a valve somewhere in which his suppressing the sound, if anyone knows the source of this low rpm restriction, please do tell. I strongly feel this will give me that close to stock purr a lot of us are looking for.