Usually called FSM around here. The NICS system isn't something I know much about but most other brands of the era that used similar systems are generally pretty simple vac control sometimes with an electronic and/or a temperature sensing switch in the path fo the vacuum lines. And generally speaking if it fails open you lose some bottom end power and it it fails closed, not sounding like your issues.
I can tell you that most fo the ecu's use the same basic batch of sensors and enrichments. First thing I'd do is check the ignition timing, then I'd check the ecu for codes. Off idle problems usually are a tps or maf issue. Often these issues are the result of dirty or wet electrical connectors so cleaning the contacts is a cheap thing to try. I have also seen fuel pumps produce enough fuel for idle then when the vacuum raises the fuel pressure the pump just shuts off.
Often people mistake an over abundance of fuel for lack of fuel. If the O2 or CHTS fail or lose connection the ecu adds fuel and in some cases it can be so much that it floods the engine. Certainly worth checking connections at both of these sensors while you are at it.
Please do follow up and let us know what you find.
Our collection of FSM's
http://www.nicoclub.com/nissan-service-manuals