Back in April, I failed Colorado emissions for high NOx. There was a thread all about it, but it got lost in the May crash. Here's a brief recap.
I bought my '85 245 GLT KJet in April of 2015. The cat had been deleted and I failed the CO Emissions visual check, but barely passed the actual emissions. I added a used cat to pass visual, plus it improved the HC & CO, but did almost nothing for NOx. I ran the KJet setup, with the original ~330K mile engine, for a few years. In early 2019, I swapped in a rebuilt B21FT and converted from KJet to LH2.4 ('937 ECU / '148 EZK / green 30lb turbo injectors and r-pack). This failed emissions in April of this year for high NOx (the CO limits dropped from 4.5 grams-per-mile to 3.5 GPM at the start of the year). Before replacing the cat, I had a free retest that was about to expire, so I re-ran with -6deg of EZK advance. This still failed, but did have better NOx.
After replacing the cat, HC and CO emissions were reduced by ~90% and NOx went almost to zero! Hence why I think there's something fundamentally off with your setup and new cat.
Colorado uses an IM240 4-minute dyno mixed driving test for emissions, and measures average GPM grams/mile of pollutants over the test. Sorry, there's not an easy way to convert GPM to PPM.
Colorado IM240 Emissions Testing Results:
<table><tr><td></td><td></td><td>4/18/15</td><td>4/25/15</td><td>4/15/17</td><td>4/9/22</td><td>4/16/22</td><td>4/23/22</td></tr><tr><td></td><td>Limits</td><td>NoCat</td><td>UsedCat</td><td>StillKjet</td><td>LH2.4</td><td>-6deg</td><td>NewCat</td></tr><tr><td>HC GPM</td><td>2.50</td><td>2.47</td><td>1.35</td><td>0.85</td><td>0.59</td><td>0.56</td><td>0.053</td></tr><tr><td>CO GPM</td><td>20.0</td><td>19.7</td><td>12.4</td><td>10.7</td><td>9.6</td><td>8.7</td><td>0.94</td></tr><tr><td>CO2 GPM</td><td>n/a</td><td>403</td><td>407</td><td>424</td><td>404</td><td>424</td><td>424</td></tr><tr><td>NOx GPM</td><td>4.50</td><td>4.37</td><td>4.21</td><td>4.48</td><td>5.52</td><td>4.53</td><td>0.0026</td></tr></table>
Here's the first IM240 failure chart from April:
And here's the matching ECU/EZK log:
(Sorry, they can't give out the IM240 chart if it passes. I'd have loved to see what it looked like.)
-Bob