98 Impreza Outback with 208k. Have replaced front calipers & pads, rotors seem ok. At low speed when braking I get a twang sound & sensation thru the brake pedal that it grabs then release & grab. If I remove the 20amp fuse for the ABS, the brakes act normal. All wheel sensors have the same ohm level. Any ideas on what this is or how to diagnose?