I don't have a photo editing utility handy so I can't circle the EGR valve but it's the device at the center of the photo.



The EGR valve is attached to the mixing pipe by two bolts that take a 6mm hex bit. It receives exhaust gas through the accordion pipe. The accordion piple is held to the exhaust manifold and EGR valve by a clamp fastened by a bolt that takes a 10mm socket.

There are a number of ways to disable the EGR valve, which is why, I presume, you're asking where it is :

1) Disconnect and cap the hose attached to the EGR valve. No need to cap the EGR valve end. This does little if the EGR valve is leaking.
2) Slip a solid plate between the EGR valve and the mixing pipe. Exhaust gas cannot get past the EGR valve to the mixing pipe.
3) Cap the exhaust manifold port. Exhaust gas cannot get past the exhaust manifold.
4) [off photo] Disconnect the two plastic lines that go towards the right headlight from the 5-way splitter beside the upper radiator hose. Cap the open ends of the fitting. No need to cap the lines. Or keep the lines connected to the fitting but cauterize the ends or slip a ball bearing to block airflow.

Why two lines? The other line serves the ARV which is less useful than EGR. The ARV is the device below the EGR valve. It redirects boost pressure from the compressor outlet to the compressor inlet. It supposedly softens the onset of boost which helps the trap oxidizer get to operating temperature. Since MB removed trap oxidizers from these cars under recall, there's not much sense in keeping ARV functional.

Do a search on EGR kit. A forum member offers or used to offer a kit that capped and exhaust manifold and mixing pipe so you can keep the EGR valve at home.

Sixto
87 300D