Fiat Ducato I purchased in December - when it goes up to 60 mph it gives off white smoke, speed reduces and it jerks along. Speed goes up and down, will not accelerate, when pressing on the gas. Have tried changing feul and oil filters but this has not made any difference - can anybody advise?

Hmmm, normally white smoke is actually steam. usual problem is water getting in to the combustion process, possibly head gasket. Do you have to top up the water in the header tank?