Someone help me with this Nox
a fouled injector. NOx comes from hot, lean and high
compression.
At 13 years old you're well past where I've seen
silted-up injectors become a problem.
You could also set the fans up to run low speed
all the time and high speed at anything over
thermostat normal idle temps (what you see on
coast-down from rolling, or at idle with low fans
running). That would fix the "hot" part of the
problem, but you still need to find the lean hole.
Reading plugs might show you. An injector clean
& flow service would set you back 10-20 bucks
an injector I expect, and identify any that are no
good after a proper cleaning.

