96 t100 I went to smog it and it failed on nox 600was max and I got 946 on the 15mph test on the 25 I barley passed the other numbers look fine just nox I live in California my truck is a California truck but no egr I have not had it very long . I don't know t he history of the vehicle at all could it be a different motor . I know the original cat is there it has 230k on it. I have sea foam in the gas tank right now replaced the spark plugs with ngk irdeuim .44 gap the plugs that came out where not the right ones and it runs excellent. Any comments advice would help thanks.