my bmw 2002 330i has a hissing sound when pressing the brakes and when it's idle on 2002 BMW 330i

what needs to be fixed and what"s the cost?

Asked by for the 2002 BMW 330i
sounds like you have a vacuum leak or a brake booster is your pedal hard when you brake?
thank you
1 more answer , 1 more comment
Brake booster Dont know the cost
thank you