My guess would be that the turbo wastegate is not operating, which means that excessive turbo boost is being created. The engine management ECU then takes action by reducing engine power before damage occurs.

The wastegate is operated by a vacuum diaphragm which receives vacuum from an ECU controlled valve located beside the battery. The source of the vacuum is from the pump which is driven off the camshaft at the back of the cylinder head. If you know anyone with a Mityvac tool you can check to make sure the wastegate diaphragm actuator works and there are no vacuum leaks anywhere, which if there were would cause this problem.

Two options. Either the vacuum hose to the turbo is kinked, or the EGR is clogged.

The vacuum host is easy to check, it normally kinks where the hose bends round the rocker cover, underneath the plastic engine cover on the left hand side of the engine. Just lift the pipe out of the channel it'll be in, and let it lie across the rocker cover.

The EGR is a nightmare to clean, and get resealed, so best left to a decent mechanic.