Stock Brake System Question

[Dwayne Cosby <dccosby@interlog.com>]

I've got a quick (and likely expensive) question on the stock UrS4 brake
system.

I've noticed that if I rapidly pump the brake pedal while the engine is
running, the brake light will come on after 20-30 rapid pumps. Also the
pedal feel is inconsistent - one minute its hard (like it should be) and
the next its on the soft side.

The bomb checks out (about 28+ pumps till hard). Doesn't seem to be
leaking fluid.

I first noticed the problem after I did my last pad swap and flush (2
weeks ago). I used a Mityvac vacuum pump to bleed the lines and managed to
suck out a fair bit of gunk as well. 

I've also noticed a quiet and constant "fluid flow" sound coming from the
pedal area if I hold the pedal about at the 90% point. This might have
always been there and I never noticed. 

Any ideas? Have I clogged some mystery line with a screen in it? Brake
servo gone bad (can someone explain the servo's purpose)? Master? Slave? 

Thanks,
Dwayne
94 UrS4