16618 - Boost Pressure Regulation: Limit Exceeded (Overboost Condition)

Hello all,My Passat 2.0tdi 105 B6 model has been going in to limp mode a few times when driving on the motorway usally at going uphill- pulling over on the hard shoulder and restarting the car has sorted it out when VCDS scanned- it came up with 16618 - Boost Pressure Regulation: Limit Exceeded (Overboost Condition), I've read a few posts with people suggesting N75 valve or sticking vanes-but does anyone know B6 specific information