I would make sure your thermo valve is working so that the EGR is actually opening under usage. Of course verifying the vacuum lines. Make sure you are in closed loop when warm under load with a volt meter on the O2 sensor.

The camshaft will affect NOX. Less overlap (smaller cam for more tq) reduces the amount of residual exhaust gas left in the combustion chamber at low and intermediate speeds. This will raise combustion temps. Camshafts were modified with more overlap way back when to reduce NOX. This is a built in EGR system and predates the external valves.

You can also look at you dist for stretched out springs and or a loose advance mechanism.

Also look for vacuum leaks.

can you post the other numbers from the test ?

Kevin