Corsa C 1.3 Diesel Strange problem?

My car drives fine, revs freely no problems, nor warning lights etc. Except as soon as I accelerate sharply as soon as the revs get to around 3k, the car gives a short judder and then I struggle to get any power or it to rev over 2.5k. It is almost like the turbo switches off as if I am going downhill and there is no load on the engine it does rev up ok. Funny thing is you stop, switch off and on, it seems fine again until the next bit of hard acceleration. No warning lights at all, I am assuming electrical, but where should I start?