Emissions problem

I have a 92 Honda Accord that I just took in to get a safety and emmissions done and everything passed except for the Nitrous Oxide test at 25 mph. The Nitrous Oxide at 15 mph was only 136 with a max limit of 838. At 25 mph it was 1195 with a limit of 759. All other readings passes easily. I wonder if this is a common problem and if there is an easy fix or trick that anyone knows of to avoid having a diagnostic test done to determine what the problem may be. Do any of you think that the reading could be off? Please advise. Thanks.

let me ask you one Q? y are u running your car through an emissions test with N2O?

spend money on diagnostics! be smart!