meexi - EGR pipe is at the back of the engine, visible when you remove the air filter box. You can see where it goes into the engine before dismantling anything by looking for a bare metal pipe at the left side of the inlet manifold, near the round wiring connector top-left of engine bay.
Glad Mick's advice about the EGR has helped someone else too, Ian. Got to say, my pipe wasn't as bad as yours, but the inside of the inlet manifold looked caked badly. The EGR valve itself was fairly coked up though and took me ages to clean. Did you enjoy getting to the 2 bolts that secure the EGR valve in place? I found them a bugger to put back in while trying to keep the metal gasket in place - used a make-up mirror to help me see it in the end.
Surprised to hear it cured the rattle. It was driving the work's Citroen Nemo that got me expecting so much more of our car in terms of quietness I think - it's very quiet and no rattle when accelerating or any other time. It has the 1.4 8-valve HDi engine in it rather than the 16V version we have in our C3s. The C3 here still has the rattle as badly and loudly as before I touched the EGR valve and pipe.
These EGR things seem a silly idea. What's happening when those large and very hard carbon chunks are going into the cylinders, and what kind of similar build-up is happening inside the inlet manifold feeds and the valve stems and faces?
I want to remove the inlet manifold at some point in the future to give it a good clean since it looked well and truly coated in black gunk, but the haynes manual says the injector pipes must be replaced after being disturbed - the Citroen service website shows them as costing £67 per pair, that's £134 for all four pipes!
Is it really vital that they are replaced once removed, does anyone know (or has found out for good or bad)?