| Check your EGR system: the solenoid, the valve, the tubes (are they clogged). A clogged and/or failing system can cause high NOx. If you still have your AIV system, make sure you have the vacuum hoses to the correct places. Check your timing. Too much timing can cause higher NOx. Which spark plugs do you have? Use proper heat range plugs. As pieboy100 says, put your cats on. I had a smog test done on mine for registration on Jan 6. Passed with flying colors -- very minimum or no emissions at all. I passed without doing any maintenance.
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