I passed everything except NOx. Legal limit is 3.5 - I had a 3.57.

Any tips on getting this down .07? This is getting ridiculous, I have replaced just about everything on the list of things to replace. Just need a quick tip to get this thing through. Any help would be appreciated!

 

read this, link but backing off a couple degrees on the ignition timing advance and enriching up the fuel/air mix just a bit will usually reduce the NOX
verify your EGR functions
you might also want to try a 160f T-stat as lower coolant temps tend to reduce NOX
http://forum.grumpysperformance.com/...on+test#p18430

 

The EPA wants you to give up and go buy a new vehicle so it will help provide union jobs and increase revenue for the government.


NOx comes from very efficient combustion, so apparently your engine is running very well and happy. EGR is used to reduce combustion heat and efficiency by slowing down the burn rate and lowering the effective VE of the engine. More EGR flow = less NOx.
If your EGR passages are partially clogged, that could easily be remedied.
Also, as was mentioned, less spark advance will also reduce combustion efficiency and lower the NOx output. Between 2* and 4* should be enough to do it. If your engine was running at 200*F or 220*F, then it may help to lower the temp down by about 20*F to slightly reduce combustion efficiency. You will still run in closed-loop, but the part-throttle burn rate will slow down by a small amount.