Did you just buy the car?
Reason I ask is that most people complain about this on the Z4M's,
It takes a little getting used to but you should be able to stop doing it,
I can tell you the CDV was done on my car within the first few days of taking delivery and I do believe it helps a lot,
The CDV slows down the clutch release and it would make sense that it could cause the grind,
I wouldn't remove it, a company called Zechausen Racing sells a modified valve that on visual inspection under the car appears to be stock,
http://www.zeckhausen.com/BMW/Z4-M_Coupe_Roadster.htm
According to board members some dealers get "funny" when it comes to any modifications, at least if it looks stock it doesn't throw up a red flag,
My dealer is too stupid to even notice such a thing,