EGR valve in 2.0HDi (Peugeot Citroen), 2.0TDCi (Ford) and 2.0D (Volvo) engine is responsible for emission, shorter engine warm up time, smoother turning off and VNT turbocharger spool down on idle. Valve clogged with soot can not close as should or even get stuck which can cause engine management light to turn on. That's why you should take care of your EGR valve, clean it and don't blank it.
This engine can be found in cars:
Citroen/Peugeot (DW10 BTED4): C4, C4 Picasso, C5, C8, Jumpy / Dispatch, 307, 308, 407, 508, 607, 807, Expert.
Ford (G6DB, QXBA, QXWB, QXWA): Focus MK2, C-Max, Galaxy, Kuga, S-Max, Mondeo MK4.
Volvo (D4204T): C30, C70 II, S40 II, S80 II, V50, V70 III.
Other: Fiat Scudo, Fiat Ulisse, Lancia Phedra.