A4 Avant SBrake servo Vacuum

[sandisonp]

Hi i have an A4 avant 1.9 TDI which currently has 135k on the clock i love the car its served me well, recently there is a wheeze on tickover and investigations say it is the vacuum seal on the brake servo unit, i am not mechanical there appears to be no detriment to braking or perfomance, the noise is slightly more laboured if climate is on as well, just sounds like a diaphragm leaking on intake or exhaust can anyone advise of a fix easy or major or any info would be appreciated

first posting ever:p