I have a sinking brake pedal on my '94 9K CSE - I went to the Saabsite.com, and find this for non-ABS:
"when sitting at a stop sign or stop light with your foot on the brake pedal that the pedal seems to continue to move toward the floor very slowly. The rubber seals in the master cylinder tend to wear around the edges causing leaking past the seals. Replacement of the master cylinder is the repair"
So what is the likely failed part for an ABS system? The accumulator?