ok, heres a shot in the dark, from the school of "been there, done that, got crucified by a new part".
Rear Brake Compensator is screwed. The result is that the brakes just aren't sharp, and in a dire emergencies, or just simply braking, you need to turn to prayer to stop, rather than trusting your brakes.
This component has about 17 different names. You have been warned.
If it is my rear brake compensator thats buggered i'll tell you all when the car returns.
Tin