Exhaust
Gas
Recirculation Valve

EGR Valves help to reduce engine temps and emissions by introducing small amounts of already burnt gasses into the combustion chamber during certain times of the engine running.

An emission's control device deamed unnecessary on some vehicles as percieved by Nissan. The emissions were controlled in other ways on some models.

Look on the left side exhaust manifold, see if there is a thick metal tube going from the manifold to the intake, via a valve with a vacuum diaphram on top of it. If there isn't one there, then you don't have it. If don't have it, don't panic, you have a model that didn't need it.