breaking system

I have a 1995 olds cieara when you step on the breaks the car pulsates
can't feel it in the pedal. changed the front rotors and pads and changed the rear shoes and drums still there.Was wondering if it could have anything to do with the ABS system. Really starting to get under my skin. please help someone before i take the bridge

Hi.. We are having a issue with our braking system on a 41 Chevy streetrod. We've got a real soft brake pedal. Have changed the master cylinder, brake booster, and calipers. When you pinch off the brake line at the calipers (front brakes) you get a great pedal, but as soon as you release the pinch the pedal goes soft again...any ideas on what is causing this?? It has a whole group of us stumped!
Thanks...