Joe

Hi, think Kevin is making the point that that smoke test is a low positive pressure and the inlet works under vacuum. Therefore one way valves can isolate parts of the system which may still leak under vacuum.

Servo pipes are a common fault on VAG, along with breather pipes which may be masked by PCV valve. The PCV valve it self can also cause problems it self with out showing a external leak.

Is the EGR operated by vacuum or Electric ?

Cheers Aidan