[jk1000]

Sounds more like the crankcase breather. One end of the "small metal box" connects to the air cleaner and the other end fits into a hole in the valve cover on the driver's side.

As mentioned by submariner409, the EGR is attached to the intake manifold and controls NOX. It's located at the passenger side, rear of the intake manifold. It has a vacuum hose attached to it.

As far as CO, that is purely a mixture problem (too rich). Adjusting the needle valves (inward) on the carburetor should help. How much? I don't know. A carb rebuild will probably help too. The solid floats tend to absorb fuel over time. This makes it somewhat heavier, and will raise the fuel level in the float bowl. This too, equals a richer mixture.

Also, make sure the engine is fully warmed up and the choke fully open before your emissions test.

No CATS on a 72. Hmmmm, maybe you could put one on (temporarily). That would probably clean things up enough to pass.

Emissions testing sucks and really should not be required on a vehicle that age. Never mind the diesels spewing huge clouds of black smoke. Let's pick on the antique vehicle owner that only drives a few miles each year.

Good luck and get that exemption. Let us know what happens.