Citroen C3 1.4 Hdi 8V lack of power / acceleration?

I have a 04 reg 1.4 hdi c3 which has a lack of power / acceleration. I have checked a/ changed various things like egr velve, egr control valve. There are no lights on the dashboard and no error codes on diagnostic.
Could anybody suggest any other things to try or has anybody else had this problem and been able to resolve it