I have a 2L Hdi 306 (same engine) and a lot of people remove the EGR completely. I will be doing that and removing the cat to get me about 5 more bhp and increase mpg. Mines a 51 plate so this may be different on later ones.
you can clean them but its only a short term fix. If you clean/replace it you will probably find the light will go out after three turns of the ignition if the fault has gone.