erratic and intermittent loss of power in brake system

What is your question?

when approaching a stop where i have need to coast for a longer distance with foot on the brake i often lose power braking before i come to a full stop. when this happens it is very similar to a vacuum assist brake system that has lost all vacuum boost. i have replaced the power steering pump and the hydra-boost twice with no affect. when this happens the power steering is not affected.