Originally Posted by hey_allen

If it has one, it's most likely on the left exhaust manifold, just to the rear of the front cylinder. If you don't have it, there is likely a flat bolt head in the hole, plugging it.

On my m117 engines, the EGR has a ~1/2" pipe curving up from where it is fastened into the header, and into the EGR valve mounted on a bracket attached to the manifold. There is another ~1/2" pipe running from the rear of the valve, around the back end of the left head, and then back forward under the intake manifold to dump just under the throttle body.

If you do have the EGR valve, and are failing for an EGR related fault, it's possible (or even likely) that the end in the intake manifold has become plugged with carbon.

I haven't cleaned mine out yet, but I've heard of owners of the newer MB's removing the valve and using a piece of cable to "roto-rooter" the carbon plug out by stuffing the cable down the pipe and spinning it with a drill to knock it all free.

My only concern would be what it might do to the engine by ingesting the small chunks of carbon, but I might be worrying too much on that.