98 Forerunner failed Ca emissions 73k miles

Nox was 975 average is 625 HC also hi.....could this be the Oxygen sensors?
Or what else?...3.4 litre 1 exaust pipe. I understand most have 2?

Change the o2 sensor before the cat converter and it should pass fine

Make sure you get the correct sensor. CA vehicles have a Air/Fuel ratio sensor. Take your VIN to a dealer to get a part number.