The brief
The Sharan had gone flat, down on power with a check engine light, the signs of a turbo boost leak. It came up on a preventive maintenance check, exactly the kind of wear a regular service is meant to catch before it strands you. On a turbocharged engine the turbo pumps pressurised air through a run of charge pipes and hoses to the intake, sealed at each joint with a collar or clamp. Those hoses are rubber and they heat-cycle under pressure, so over the years one splits or perishes, and the collar that seals it hardens and lets go, and now boost is leaking out before it reaches the engine. The engine never builds the pressure it expects, so it feels flat and the management lights the dash. A split hose and a perished collar don't reseal, so they need renewing.
The diagnosis
Diagnostics confirmed underboost and boost-deviation fault codes, and a check found a turbo charge hose split and its collar perished, bleeding boost pressure, which is exactly the flat feel and the light. The turbo itself, the intercooler and the rest of the pipework checked out. So it was a hose-and-collar replacement, fresh rubber and a new clamp where the old had failed, then the codes cleared.
The work
The split turbo charge hose was removed along with the perished collar, and a new genuine VW-spec hose fitted with a new clamp, the other joints in the boost pipework checked while everything was apart. The fault codes were cleared and the engine's boost adaptations reset so it could relearn against a sealed system. A road test confirmed strong, clean boost, the flat spot gone, and the light staying off.
The outcome
Strong boost, clean throttle response, the flat feel gone, and no warning light. The Sharan went home with the turbo system sealed and pulling properly again. A split charge hose robs the engine of its boost and only gets worse, so renewing the hose and the collar and letting the engine relearn put the power back, the kind of wear the maintenance check is there to catch.