I have a 2004 Renault megance dci engine.

It`s not engine-threating but it can produce ECU faults sometimes going into "limp" mode. It is possible to by-pass the EGR (Exhaust Gas Re-Circulating) valve but I`m not sure how on this vehicle.

Check with GSF or Euro Car Parts for new parts. I`ve only ever gone to a dealership as a last resort.
The parts from these places are generally made by the same people who make them as OEM (Original Equipment Manufacturer). The old term was "pirate" spares but nowadays, aftermarket stuff is as good as
OEM.