Spongy brake on '91 100

[Tak Cheung <tcheung@gandalf.rutgers.edu>]

Lately, the brake pedal seems a bit spongy and if I step really hard on it
at a stop light, the pedal kinda sinks slowly to a stop.

The car seems to stop ok however, but I don't particularly like to let it go
on like that.  Is this a sign of the master cylinder going ?  

This is my first Audi with ABS brakes, don't think it's due to that is it ?

The hydralic system seems ok however, my pwr steering works, so I presume the
brake booster is working as well.  There isn't any leak in the hydralic line
as yet and the hydraulic fluid level hasn't dropped due to any leak that I can
detect.

Any suggestions other than have the shop take a look ??

Tak Cheung
'91 100
'92 Saab 9000S