Hi Snake,
From reading the posts on E90 Post it seems fairly simple to me.
Remove the pipe from the exhaust, insert tiny ball bearing and replace - job done, valve remains permanently open providing a louder idle etc.
The BB's arrived today... tiny little feckers, hope they are big enough - I did order the size recommended on E90 Post and on here - 5/32 inch....
Will send out as soon as I receive SAE's
pm me if you are interested.
Cheers
moff