SENSOR PROBLEM OR ELECTRICAL PROBLEM?

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while accelerating hard yesterday the car suddenly gave a jerk as thoough the engine had cut out for a fraction of a second
i slowed down pulled over and put it in neutral and felt as though the car was bouncing
the acceleration was very slow but i reached 70 eventually which made me think it was in a mode that enables you to get home but not at any great speed
i turned car off then restarted it 50% of acceleration has returned but still jerky when accelerating hard
the car will cruise quite happily at 100mph but its getting there that takes ages
if you accelerate more gently there doesnt seem to be any problems
thought it may be sensor or the gearbox or even the kompressor
any ideas anyone?
thanks