Engine check light lit & need to replace Catalytic conve

Hi, I have a 1999 Acura 3.2 TL with 123,000 miles. The engine check light was lit. Last week I took it to smog check and the mechanic told me it failed and needed to be replaced both catalytic converter and oxygen sensor and it will cost me about $1,000. I took the car to another mechanic. He read the result and told me that all emission test had indicate a 'pass' and with the most excellent numbers
(15 MPH: RPM:1659, Co2%:14.4, o2%:0.6, HC(PPM):0, co%:0.00, NO(PPM):0, PASS)
(25 MPH: RPM:1650, Co2%:14.4, o2%:0.6, HC(PPM):0, co%:0.01, NO(PPM):16, PASS).
And the only problem is 'Malfunction Indicator Light' showed 'Fail' with a fault code of 'P0420'.
Question: if catalytic converter and oxygen sensor failed then emission should fail, but my test showed 'pass' with excellent numbers.
What should I do? Fight DMV and Acura? :X