2003 Civic failed the NOx..
 

the readings were as follows ( Car is a DX manual )

Limit Actual
505ppm 772ppm

When I picked up the car it had a cracked exhaust manifold, so the first order of things was to pick up a new manifold, which just happens to have a brand new CAT attached to it. Upon failing test I pulled plugs ( I will note plugs were not very tight in the head at all)
and found the gaps to be worn to about twice what the factory spec should be. I tried to test the O2's, however my multimeter doesn't seem to be sensitive enough to pick up proper voltage. I do not have any MIL's showing. I added 1 bottle of redline Si to a full tank, just in case injectors are fowled. Any other insight on the situation would be much appreciated.

Matt

Turned out my problem was a faulty (brand new) Cat converter....