03 Focus St 170 Engine Fault

hi, my 03 focus st 170 has the management light on it has been to a ford main dealer who could not sort the problem, 3 other mechanics have looked at it but the light is still on it has had a cam sensor a camshaft sprocket,intake manifold flap control unit and an airflow meter. the fault comes up as variable valve timing to far advanced.it starts and drives ok but you need to build the revs up to get it to pick up. if i drive on a long trip after about 80 miles you cant put your foot down more than an inch or it trys to cut out but if you stop for a while its okay again can anyone please help me its doing my head in.
many thanks
john