Originally Posted by BillGrissom

Rollguy here sells an affordable kit of block-off plates if you remove the EGR, or at least did when I bought one for my two 300D's. Not to scare you, but perhaps the innards of your intake manifold look similarly occluded with gunk. A common problem with diesels and the newish direct-injection gas engines. I understand for the later, manufacturers are beginning to add a small upstream fuel injector to keep the intake clean. As is, DI owners must remove their intake for a good cleaning every 50K miles, which isn't cheap. Goss's Garage on Motorweek discussed it.