1994 Acura Integra Emission test failed

I have been reading alot of these questions regarding cars not passing the smog test, due to high levels in nox. My acura integra did not pass nox at the 15mph mark, but did pass at the 25mph mark, and so did everything else pass, I am aware that, the most common problem can be the egr valve, then the catalytic converter, but my car, (1994 integra ls 1.4 dohc) does not have an egr valve, this particular model doesnt require one, so does that mean its automatically gonna be the catylitic converter, or oxygen censor. Anything will help, thanks, it is well appreciated