2008 A6 Sensitive Break Issue
 

I've recently purchased a 2008 A6 Quattro 3.2 w/ 108,000-ish miles. Most everything works as expected. My brakes (and transmission and idle which I will wait to discuss) have been giving me fits. Although it may have been this way when I bought it (from an Audi dealer), it seems my braking problem is more and more noticeable as time passes. I've seen a thread describing my issue, in a round about sort of way, as a lack of control or modulation. They seem to 'engage' too quickly and as I continue to apply pressure, there is a jerking as if the brakes are grabbing (it correlates to brake pedal movement, jerking, not as if I'm apply consistent pressure and it jerks anyway). In contrast to my 2008 Jetta, when I apply the brakes, no matter the speed, I have to press progressively harder to get more braking power (this is true in the A6 as well, but much too quickly). The latter seems normal to me. Another 'symptom' is that I seem to be going through pad material quickly. In only a day or two, break dust covers my rims (noticeably a different color but not completelycovered). Looking at the CARFAX, this car is on it's 3rd pair of front rotors (which if it's true means I'll need another set of front rotors the next time I replace pads) and second rear set (not too surprising). I'm not sure I can necessarily see that there is a systemic problem with the brakes based on the amount of miles between pad changes though. Any help/advice is appreciated. Thanks!

I tried cleaning and, although it seemed to work, ended up doing nothing. I'm still having problems and would really like to hear from anyone who may have had a similar problem and what they did that fixed it. Does anyone think it's my calipers? Or air in the brake lines? Just looking for some help. What about the Master Cylinder? Thanks.