I am having a problem with my hydra booster type ABS brake system.

What is your question?

when I apply pressure on my brake pedal to stop sometimes the pedal is hard to apply and the is hard to stop. Other times there no symptoms..I just replaced my brake hydra booster with a AC Delco reman. I flushed the p.strg fluid out several times, I still have the hard pedal intermittently. Any suggestion will be greatly appreciated. please respond to tautomotive@hotmail.com thanks in advance to whom ever is reading this tlee13