I have a '93 3000GT SL ~ front and rear are braking unevenly. infact, it's almost as if the rear brakes aren't doing much of anything. i put new rotors and pads all around about 6 months ago. when i starting to notice a scraping sound from the front, i took it apart again and found that the front pads were worn almost to the metal while the rears were almost untouched. after this, i rebuilt all four calipers and put on new pads again. i'm still getting grinding/mild squealing sounds and the pedal is pumping back when i brake. i'm not sure what the problem could be ... please help ....

thanks