Khaled, I still have my M5 and ASR CAI is still one of my favorite mods. The one for sale is from a friends car that is beying traded back for an X5. The foam from the air bypass valve on the driver side is worn due to rubbing fron his badly fitted wheels and needs replacing. The driver side is really only consmetic, but to be fair I posted as both requiring replacement. The M5 and M6 CAI is identical as the intakes on both cars are identical. I know because I installed the one on my M5 and his on his M6. Also,I used my M5 parts to put the M6 back to stock. I gave up my stock parts because I am never going back.
Regarding performance, I am very happy with my CAI and he was very happy with his CAI. Literally, one of the best mods I put on my car, and I have quite a few. At 3500 rpm's the car really comes alive. Then with headers on, at 5000 rpms the car wants to jump out of its paint.