1995Berretta

Does anyone know anything about the Power Master III ABS system?

I am having trouble with the system in my car. My car is actually a 1991 Olds. Cutlass Convertable. But there is no one on the Olds Forums that know anything about the system.
I know GM used it in alot of the cars with ABS in the early 90's

The brakes kind of went away. Talked to an old GM master tech (That I cant reach now)
Replaced the accumilator which fit what I had wrong at the time.
Then tried to bleed the brake system according to the Factory service manual. The rear bleeder snapped off in the calipers. So I replaced the rear calipers and bled the system.

Drove the car about 10 miles then the brakes started acting up again. When I first press the pedal it is hard then after about 5 seconds it will release and the car will almost lock up the brakes. I need to try to figure this out and get it fixed to be able to drive it on Tuesday.

Please anyone that has any Ideas please post I really appreciate it.

Thanks for any info at all.