Citroen xara probs?

I am still experiencing probs wi the above, in that the warning lights regarding the engine management system are coming on and the car sometimes stops, it feels as though the car loses power briefly and then picks up again the orange light comes up on the display. The oil light also comes on stating that the pressure is low its been checked and is ok, and the sensor switch has been replaced, its been diagnostically checked twice no faults were stored, the central locking is working intermittently, are these faults related or could it actually be the brain thats faulty, please help at the end of my patience wi it!!!