AZ must not be stringent enough on NOX then or federal emissioned LB7s have a much higher limit on NOX. Every time ive taken my truck through testing, its been on some sort of tune (edge on lvl 3 the first year, PPE on lvl 3 the next, this custom tow tune from steve this past year). All but this past year have passed with flying colors. This past year, the retards at the facility could not get the truck to show a reading on the computer with their sniffer. the claimed it was cause my exhaust dumped under the truck yet it passed all years prior. After 4 runs they gave me a "directors cert" saying i was exempt from testing for 1 year.
IIRC, NOX level for my truck can not exceed 40ppm. ive always hit 20 or below. wish i had a stock reading to compare too but by the time i was required to test, it was already tuned.
im curious to see what someone could and could not do with tuning and emissions. it would be a cool test IMOP. out here all we get is "wait itll the green light, hold it floored for 5 sec, then let off".
Is that NOx or particulate matter? It sounds like they are testing your particulate matter/soot output...not NOx. 20ppm NOx is incredibly low. IIRC the NOx sensors on the LML's can only read down to ~100ppm minimum.
I dont know of any places testing diesel exhaust for NOx....im pretty sure its particulate matter only.