Have now booked it with another audi specialist who seems to have assured me that he will get to the root of the problem.He spoke of doing a "smoke test" to find the leak. Will let you know how i get on.thanks for the reply.

 

smoke test is a good boost leak indicator. sounds like she knows a thing or two. good luck.

 

Lets hope so,keep u posted. Thanks

 

Job done,found leak straight away.turns out to be a cut servo pipe.I'm amazed that the other so called audi experts could nt find the leak,especially after seeing the size of the split.many thanks everyone for your help.

 

Job done.leak in pipe found straight away.Was a split in the servo pipe and after having seen the split i am amazed that the other garages could'nt find it.thanks for all help everyone.