Ford Repair: 1998 winstar abs braking, winstar, vibration

Question
Problem when applying steady pressure to brake petal will suddenly start to fall away and you will have to pump brake.
Abs light will come on garage says code indicates abs problem.
Have replaced master cyclinder, abs Pump (?) with used part and bleed brakes several times.

Answer
If you don't tell me the code I can't help you accurately.
Used parts may be cheaper, but can have similar problems to what you already have. ABS problems will typically cause a hard pedal, ABS activity when it isn't needed, or what feels like a vibration in the pedal.