Did anyone ever find out if the cracked carbon fiber affected performance or was it merely cosmetic? My M3 has cracked as well. I hate that I bought it on ebay so I dont have a dealer to return it too. Hoping that it is just cosmetic.
I had the same issue with mine last week. I was cleaning my club and noticed that I had the same cracks in the same location. Luckily my local shop took it in on the warranty and replaced it on the spot for me.
As far as performance and sound, I had not noticed any difference before finding the crack. The funny thing was I hit my longest drive of the year on the 18th hole the day before I noticed the crack. This is why I found no performance issues with it.