1998 dodge neon

.  my car failed smog check today.   the reason is the no     ppm was too high  .   m1    15 mph   rpm 1812    co2    max 14.5  %o2   0.0     hc  ppm max  64 ave 9  meas   7     co%   max  0.55     ave 0.03   meas 0.13    no   ppm     max   4.77     ave 67     meas525      result     fail

i replaced plugs .oil and air filter,oil ,one fuel injector prior to the test. tested spark plug wires   .

the idle seemed too fast. i adjusted to lower speed but it still seemed too high.   i just had the transmission rebuilt . i  put in a used fuel pump. changed temp sensor. checked all vacuum lines,  changed the dash gauges.

i did not change the smog valve .  could this cause failure??    i asked the smog person at the star station what needs repair .  he said it could be anything. tired engine ,catalytic converter or something else.      what is the most likely cause of the failure please?

my care engine always seemed powerful. get up and go. one day a fluid line to my transmission burst.
i had to have the transmission rebuilt. now the car does not respond as quickly when i need to speed up to get on the freeway. also the car has failed to pass a star smog check. the ” no” level was too high at 15 mph
can they be a related problem??

what is the most likely to cause a no too high failure at the star test facility