Thanks for suggestions, will attempt to explain more clearly.
Was getting very uneven tick over about 3000 miles ago, problem was diagnosed as cracked inlet manifold, had new manifold fitted and car ran much better, decided to have remap, very pleased with result acceleration was very much improved.
Latest problem started about 300 miles ago, slight turbo lag and minimal power drop, decided to clean all sensors and electrical connections, no difference, I then decided to replace the EGR valve and fit diamond shape blanking plate. On removal of valve (sooty but not coked up) it was found that a square plate with 4 holes was already fitted, this was removed and the diamond shaped one fitted, results were mixed, ECU logged it as a fault but engine seemed to run smoother but very bad turbo response at low revs but normal at higher revs. Decided to change the blanking plates over and now I am back with a very jerky machine at low revs in traffic and a scalded cat when I put my foot down. Frustrating.