2004 Vauxhall Vectra fault code PO234 Vauxhall Vectra

My car was recently diagnosed with fault code po234 turbo overboost condition I have been told to replace turbo solonoid valve. I have tested all the pipes and they are fine no cracks in any of them the car goes into safe mode wont rev over 2500 rpm has any 1 had a similar problem and was it cured with the turbo solonoid valve others have told me it could be the maff sensor I dont wont to replace parts that I dont need replacing. The turbo itself is new and has already cost me a fortune