Help with 1997 Camry that Failed CA Smog Test Twice

Hello,

This is my first post in the forum. I have a 1997 Camry XLE (V6) with 140,000 miles on it that failed its smog test twice. Here are the results from the first test:

15 MPH, 1747 RPM
HC = 25, MAX is 52 = Pass
CO = 0.01, MAX is 0.49 = Pass
NO = 967, MAX is 424 = FAIL

25 MPH, 1736 RPM
HC = 18, MAX is 36 = Pass
CO = 0.01, MAX is 0.46 = Pass
NO = 1,115, MAX is 711 = FAIL

The test-only smog technician said I either have a failed EGR valve or failed oxygen sensors. I took the car to an independent mechanic who plugged a diagnostic into the dash. He said the EGR was dead but all the oxygen sensors were fine. He replaced the EGR valve and the car failed again. Here are the results of the second test:

15 MPH, 1754 RPM
HC = 23, MAX is 52 = Pass
CO = 0.02, MAX is 0.49 = Pass
NO = 1,213, MAX is 424 = FAIL

25 MPH, 1723 RPM
HC = 18, MAX is 36 = Pass
CO = 0.01, MAX is 0.46 = Pass
NO = 1,479, MAX is 711 = FAIL

Not only did it fail, the NO numbers got worse! I am not a mechanic. The person we used is a mechanic for the US Marines who I trust. He fixed a nagging oil leak for us in the past. I am praying this is something simple - like the unit is not connected properly. The car is being saved for my 15 year old daughter to learn on. It will barely be used - maybe 1,000 miles over the next year. Any help, suggestions would be appreciated.

P.S. I have tried contacting the Marine and have not heard back. He is normally responsive, so he may be out of town for the holiday.