Wifes 1989 supra failed inpection very very high HC and CO - could it be O2 sensor?

[ms0072]

My wife has a 1989 supra / 7mgte.

She took the car to inspection this morning and it failed smog.

Readings are

IDLE
------------

hc ppm -- reading -- 261 -- standard (220)

Co% -- reading -- 0.52 -- standard (1.20)

co2% -- reading 14.1
o2% -- reading 1.1


HIGH IDLE
--------------
hc ppm -- reading -- 2563 -- standard (220)

Co% -- reading -- 3.33 -- standard (1.20)

co2% -- reading 11.6
o2% -- reading 2.2


Any ideas what could be causing this.
The car has new plugs and wires in the the last few months, seems to idle and drive well most of the time ( she did say that there are rare times when it runs rough/poorly for a minute or two) but then it goes back to normal.


I think it has the original 02 sensor -- could that be causing such high numbers ?
How can I diagnose it in the driveway without being able to test the hc / co ?

Thanks

Any help appreciated.