I don't think we are speaking the same language here. PN 51127223162
(
https://www.ecstuning.com/b-genuine-...r/51127223162/) is *NOT* the piece that covers that hole. 640i already comes with it from the factory (26 in the diagram).
So what I need is either 27 or 22 from the diagram.
https://dz310nzuyimx0.cloudfront.net...ed0464a793.png
I only drove mine for couple miles today after the install (both valves closed) and did not notice any drone (but no highway driving yet). Like the slightly richer sound. I'll play with the valves later after I take care of the diffuser part, but I may keep the valves closed.