I've been trying to troubleshoot a Saab 900 which tests high for Nox in the California smog test. One person recommended checking the EGR system (exhaust gas recirculation) as one possible culprit. The Bently shop manual for this car shows an EGR valve, but my car doesn't have one. Its all original (I bought it new). Did the California specification model use a different system? Does anyone know what other parts of the emissions control would help lower Nox? I replaced the air mass sensor last year but am not sure what to try next. Thanks! David in San Francisco