Originally Posted by 323iMarto
You are correct, my muffler did come with the pneumatic valve on one of the pipes but serves no purpose on our cars. The default position is open so it causes no real dramas.
I'm not sure but perhaps the E90 330i that you could get from about 2005-2007 would utilise it.
I know the US version 330i from around the same time has that, so it seems quite likely.