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S4 hydraulics

Submitted for your thoughts.

Here is the scenario, went out for a drive on Saturday in the '93 S4. Brake 
light stayed on and I got a constant pulsating any time the brakes were 
applied, I also got a vibration from the front end when I wasn't on the 
brakes. Weird.

Here is why I'm seeking your advice. The car has had both the hydraulic pump 
and the brake accumulator (bomb) replaced. The PO had the dealer do the work 
and the hydraulic pump is still under warranty.

I did the "engine off pump the brakes test" and I didn't have much power 
assist. This, per the list, is indicative of a bad bomb, but if the pump has 
gone bad than the bomb will only have so many pumps left in it total (since 
the pump will not be providing pressure to "pump up" the bomb), correct?

Car has 61,500 miles on it.

On 5/24/96 at 44,480 miles Continental Audi (in CO) replaced the 
accumulator. Noted on the service order "Brake pedal will flutter and loose 
power assist intermittently, especially on hard braking." Part cost $405.

On 8/28/97 at 58,797 miles (still under warranty) the same dealer replaced 
the Hydraulic pump. Noted on the service order "Red brake warning light is 
on, pedal pulsates when in use." Part cost $432.

I'm obviously hoping it is the pump as it is under warranty. Since I'm 
having the exact same symptoms this seems to be the most likely culprit. 
Thought I'd bounce this off the list for any comments.

Could both the bomb and the pump be bad?
Could it be something else?
Does the brake light come on when the bomb goes bad?