smog failure

You have to first attend to the high HC reading fixing that may lower the NOx emission. What are the CO and or O2 readings. If CO is very low mixture could be lean. All the gas readings relate to each other, when one rises the other may lower.

HC new cat is quick ez ans. NOX is the difficult one to answer. automechanicspace.com has the best answers for NOX. P.S. I get new cat's for like $50. that cost $150. in CA.