Fault Code 16618

Hi guys,

My parents have a 55 plate Octavia 2.0TDi (PD140) Elegance. A recent fault code scan has returned code # 16618 - Boost Pressure Regulation: Limit Exceeded (Overboost Condition) : P0234.

I was wondering what the possible causes of this could be? The car's only driven gently since they've had it, so I was wondering if the turbo had got a bit "gungey", causing the vanes to stick and needing a clean? If so, would a brisk run up the motorway sort it, or would that be potentially dangerous? Ross-Tech's wiki say it could be the boost pipes, or N75 valve, but I didn't know if there were any other possibilities?

It's not trying to impersonate a police siren at the moment (the turbo has been slightly more audible recently, but we've put that down to the cold, as my Fabia has been slightly louder too). To be honest, if I hadn't have done a fault code scan, we wouldn't have known about it, as there's been no symptoms of it showing.

Thanks.