[s-cars] S4/S6 brakes

[Bill Clancy]

OK... I promise not to rant about the bad brakes.   But I would like some
help.

I think my car has unusually bad brakes.   I am not looking for brakes for
the race track.  I just want ordinary brakes like I find in any average car.

Here are the symtoms.
Pedal feels muddy
There seems to be a slight delay when applying the brakes (occasionally
almost causing me to rear someone)
It takes extra pedal pressure to stop the car

but...
If I slam on the brakes, the anti-lock works (if needed) and the car will
stop just as well as any other car..using medium pedal pressure.

Other data points:
Changing the front pads with new ones makes almost no difference at all.
Changing the rear pads will give me back great brakes, but only for a week
or so while they wear in.   Then I am left with shitty brakes again.

I almost feel like the master cylinder is defective.   maybe it engages the
rear first and wears them out, leaving me with glazed rear pads.

Do any of the symptoms above sound familiar?   Is this what others
complained about leading to bigger calipers and rotors?