Performance in M Performance?

Most of us would have bought the m performance body parts for aesthetic reasons but do they actually offer any real performance?



I am referring in particular front splitter, rear spoiler and rear diffuser. I read somewhere that Bmw does actually wind tunnel test them but I can't find the reference again.



So do these parts have measurable increases in downforce etc? I'm guessing it probably doesn't make any real difference but has anyone come across published numbers?



For the prices we pay you would hope so.