failed nox emissions...fuel pump?

I failed emissions in my jeep the other day. I passed everything except the NOX. My fuel pump has been humming badly for over a year. Would this cause a lean condition causing me to fail nox? Not sure if it is related but if I hold the jeep just above idle for about 30 seconds and then let go of the gas pedal the engine stumbles and almost quits. Thank you for your help.
Anders
88 Cherokee
4.0
218000
33s

Cylinders carbon-ed up
Inoperative EGR

Could be the EGR. Search google for EGR and NOx for some threads with test details. There is a vacuum line, an electric signal and an electric solenoid in the EGR control circuit. search does not work for 3 letter words, only 4 or more letters.

Check the fuel pressure with a fuel pressure gauge. Should be 39 psi with the vacuum line disconnected from the fuel pressure regulator (which can go bad), and about 33 psi with the vacuum line attahced to the fuel pressure regulator. Details on this are in several threads here too.

If it is running a little rich it could be overheating the CAT and causing high NOx emissions. Also if an injector is partly clogged, that cylinder can be running lean, making more NOx. Basically something is either running too lean, too hot, or the EGR cicuit is failing.