2004 Jaguar S-Type loss of power

My Jaguar has an intermitent problem. Sometimes when I try to accelerate there is a lack of power and a cloud of black smoke is blown from the off side exhaust pipe. If at this point I stop and turn off the engine then restart it the car runs ok, but the problem will reoccour ramdomly.
I have found that by running the car on primeum deisel the problem does not happen so often and when it does the smoke from the exhaust is not so black (more grey).