The egr has holes you can stick your finger in. Then push up and make sure it opens and closes without sticking. Also you might change the temp sensor and clean the connector to it. You wouldn't know if it was bad cause there is a separate sensor for the ECU and the guage as you may know. If it's bad the car could think the engine is cold, which would richen the A/F mixture and not allow the EGR to operate and lower the NOx. I've seen many many many nissans (all models) fail just due to the temp sensor. Should see 2K-3K ohms at about 70 degrees and .3K ohms (300 ohms) with the engine warmed up 180 ish. Or just replace it....less than $20 from coz. Bring cash, save yourself a buck. Too bad he isn't open on the weekends huh?
