is there anything that i can add to my diesel to try and clean inside of engine, this is on a van which just seems to be dead as a doormat its just had a service and new turbo sensor fitted but no different any ideas would be helpful

Try Redex or Millers.

I always use millers diesel power ecomax every time i fill up, mainly to try and keep the injectors at their optimum. Many feel it's a placebo effect but I've seen how ineffective injectors can become over time, so I reckon it's worth using. As for your engine, any more info on it? size, power, mileage etc.?