As discussed numerous times already (why so many threads about the same thing?) it's a function of the pad material. The M Sport has a more aggresive pad. Aggressive pads make noise and are very dusty. If you don't like it, have the pads changed to standard non-M Sport pads. Some prefer performance. Others comfort/convenience. Unfortunately, brake pad selection is an excercise in compromise. A new set of M-sport pads will not resolve this. It is not a defect or flaw.
A couple of excerpts from some pad manufacturers:
Hawk:
"Sometimes a user may experience brake noise when no maintenance is required. We call these NVH (Noise, Vibration and Harshness) issues. Brake squeal is typically caused by vibration between the brake pads, rotors, and brake calipers. Some brands of semi-metallic brakes are more likely to experience brake squeal due to the metallic ingredients in the brake pads. "
http://www.hawkperformance.com/performance/faq.php
Wilwood:
"Do you make a pad that will work equally well for both street and track use ?
A: The short answer is no pad will work "best" in both environments; there will always be a compromise in one area of operation. Pads are asked to do a number of different tasks in different situations. The following are things you should consider to help you pick the best pad.
Stopping performance when cold. How well does the pad grip on the first stop when the system is at ambient temperature?
Stopping performance when hot. How the pad reacts in higher temperature such as on the track?
Pad Life. How long will the pads last in a given driving environment?
Rotor Life. How aggressive is the pad on the rotor.
Noise. Does the pad squeal?
Dust. How much dust does the pad generate, how easy is it to clean?
If you run one pad on both the street and the track, you will have to compromise performance in one way or another on all the above. "
http://www.wilwood.com/m/techtip/Tec...aspx?id=3&no=5