My Audi A3 has an intermittent problem with the turbo. What happens is I am travelling along with the usual acceleration etc when required. Suddenly it seems to suddenly loose the ability to accelerate, it will rev with the clutch depressed. If the ignition is switched off and on again, everything is fine. I have replaced most of the pipes around it, and needless to say it is always fine when at the garage. Any ideas where to start? Many thanks,