Depends on the road speeds the tests are done at. The stock chip activates the EGR valve above 17 mph if memory serves me. An active EGR is essential for achieving low NOX test readings. In Northern Virginia they do the low speed test at 15 mph which I was having a hard time passing a few years back. So I had Marc Haibeck lower the EGR activation point to 13 mph and easily passed NOX by 150 ppm.
Hydrocarbons should not be a problem provided the engine is in good tune and the cats are working properly.
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