Brake problems on a 1998 Grand Am SE

Maintenance/Repairs
1

Hope someone can help. When you step on the brakes the car squats down in the back, usually the right side. When you let up off the break it makes a loud thunking noise, like it is releasing. If you try to stop on a hill the frontend pulsates down the hill. We have changed the brakes and all hardware twice now and have also taken it in to Brakemasters twice. They do not know how to fix the problem. Has anyone else had this problem and if so, what can we do to fix this problem? Thanks for any suggestions!