rattling noise on acceleration on peugeot 406 hdi?

Hi i have a 2000 model peugeot 406 hdi 2.0 turbo 90 ps model,i have had a problem with it for a few years and its getting worse and also annoying,it makes a rattling noise from under the bonnet when i am acclerating,its worse when it cold but can still be heard when its warm,i dont think its a mechanical noise i think its a fuel knock but i dont know what to do about it and is it common on these,i have been told that the injectors may need cleaning and the spray patterns re adjusting ?