Braking problem on Audi 100 s3

[manji]

Hi my s3 started beeping the other day and the dash popped up the brake warning light. I was about 10 miles from home so drove home. I thought it might be fluid which i topped up and it only took a lid full.

I started the car the warning on the dash or the beep did not happen so i drove it round the corner but when i went to brake it took it a while to stop. Then the warning light came on.

Now it has pressure on the brake pedal but is very slow in braking. Put it on a computer but the computer is showing no fault.

I have been told that this car has an electronic servo could it be this? any advise is welcome.

cheers