Is there any black smoke from the exhaust or any unusual noises?

On dash warning it said gearbox fault. my machanic did a diagnostic test and it read AMM,which was replaced . This seemed to solve the problem and I had 2000mls trouble free.. The same loss of power has now returned with Dash Warning , "Restricted Performance". This time diagnostic reads Turbo fault. However when computer faults are cleared the car drives perfectly till engine turn off, then the fault returnes. Honest John suggests oil feeder pipes to and from Turbos {there are 2}. Will have these checked and let you know if problem sorted

I have read that before on other forums but is not the case here