powersteering/brakes: loss of power

[Ahmad Helal]

1990 Audi 100
 
all of the sudden my powersteering comes in and out....sometimes it will loosen up and then lose power suddenly..there is no patteren...also my brakes have lost power...and sometimes they come back....after doing some research I found out that my car has a booster for both the power brakes and power steering..would this be the problem...if so..how can I test it....
 
Also any one out there have a 89-91 100/200 bentley manual or CD they aren't using anymore? (I am a college student and can't afford the retail price at this time)

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