The exact location of the EGR valve on a 1988 Dodge D100 will depend slightly on the engine type (e.g., 318, 360). However, it's generally found on the intake manifold. Look for a small, usually rectangular or canister-shaped valve with vacuum lines connected to it. It's often situated near the back of the intake manifold, sometimes relatively close to the firewall.
Because precise location varies slightly, I strongly recommend using a repair manual specific to your 1988 Dodge D100's engine. A Haynes or Chilton manual, or even a digital version, will have diagrams and photos showing its exact position. These manuals are invaluable for working on older vehicles.
