You don't have to replace anything. What is happening is brake piston on one side or the other (or both) in the rear is receding into the bore. When you press the brake, the fluid has to pump out the piston again, and your pedal feels like crap.
Check out the ogres cave, look for brakes.
I ended up using this method because the ogre's method didn't work for me (It's easy!).
1) Pull off the ebrake cables if they are still there.
2) Pull off the springs
3) Remove the e brake lever (17mm I think). This will leave you with a stud with a 13 or 14 mm nut on it close to the caliper
4) Use a 14/133mm wrench to rotate the stud via the nut. You have to be careful to rotate the passenger side clockwise, and the driver counter clockwise. It's towards the rear if that helps. The stud should appear to be coming towards the middle of the car. It will hit a 'stop' when the pads close on the rotor
5) Reinstall the ebrake lever at the closest position to reset. It's only a 6 point deal, so it could bu up to 59 degrees from the stop.Put the nut back on
6) Check for drag...you shouldn't have any. Lift the ebrake lever...it should stop before 1/2 throw
7) Reinstall ebrake hardware. Note...if you don't have a cable, still install springs to keep the levers reset!!
Now you will have good brakes...enjoy!!
[This message has been edited by Slowbuild (edited 09-23-2013).]