Hello,
Last year my Aurora failed the Smog test,(high NOx). The guy replaced the catalytic converter and it passed. This year, I was referred to the test only center for the Smog test and it again failed due to high NOx. The car has high miles, 225,000. V-8 ,4.0 engine runs great. I removed the EGR valve and cleaned the pintle to make sure it is free before the latest test. Any ideas what to try next?

Problem solved. The passage from the egr to the intake passage that feeds the intake manifold was plugged with carbon, etc. Cleared it, great SMOG test results.