Trying to figure out what causes to fail the NO (ppm) test on my kid's TOYOTA 1987 MR2

%CO 14.6 & 14.7
%O2 0.3 & 0.2
HC (ppm) 33 & 25
CO (%) 0.01 & 0.03
NO (ppm) 1115 & 735 max 825 & 764
failed the 15 mph test and barely passed the 25 mph test.

I also was told that the timing was of by 10 degrees, retarded I think but not positive.

Don't know what causes the NO emmisions, the cat was repalced two years ago, the car uses a quart of oil every 1k miles.

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Thanks, Juan