Emission Test failed

I just went for an emission test and failed, the NO reading it was three times over the Canadian limit.
The car has been running fine new plugs,oil changed,O2 sensor new DI cassette and really should have passed with no trouble.
Any idea what could be causing such a hi NO reading?
1997 Saab 900 SE Turbo with 130,000km

I just went for an emission test and failed, the NO reading it was three times over the Canadian limit.
The car has been running fine new plugs,oil changed,O2 sensor new DI cassette and really should have passed with no trouble.
Any idea what could be causing such a hi NO reading?
1997 Saab 900 SE Turbo with 130,000km

According to the following article, top considerations for high Nox:
Ignition timing (unlikely on your car IMHO)
EGR system
Catalytic converter
Carbon build-up
Too hot operating temp

http://www.wivip.com/3_5_1.PDF

(Adobe acrobat reader req'd)

Also may want to do a google search for "high nox emission" and learn more

Good luck,
Jim M