CO2 is carbon dioxide.usually hc in ppm and co in % have set maximums.in Ca the first emissions program(1980's) allowed 500ppm HC and 5%CO for older cars. if your HC level is high that is unburnt gas going out the tailpipe.if the carbs are in good shape and the needle holder in the bottom of both carbs are adjusted up already try lowering the float level to lean out the mixture.if your sending unburnt gas out the tailpipe your wasting gas and money

You might like to look through all of the information here
http://www.azdeq.gov/environ/air/vei/motor.html
If I read it correctly you should be exempt, as the car is over 25 years old.
It looks as if the reglations came into force May 1st?

I might be wrong..............

My neighbor had a VW that wouldn't pass and I offhandedly suggested that he put a catalytic converter on. We he did it and it passed. He said the smog guy said "that's a strange looking muffler". He didn't know if the guy was serious or not.
But the VW passed easily. If your desperate you could try this and remove it after the test like my neighbor.
Gary

Is it CO2 or CO that you can't pass? CO requirements are usually stated as % not ppm. HC emissions are typically ppm. For example in the Vancouver area of BC a pre 1973 4 cylinder car of 2.2 liters can emit no more than 1028 ppm of HC and 5.35% CO at idle.
If you give us the AZ. standards and your test results maybe we can see what tradeoffs might be possible.

Cheers,
--
Barry -- 1967 122S 'Betty'

They test vintage cars, how unfair...I'm not sure this will work, but back when I lived in Vancouver, BC we had to do a smog related test every year...one of the tricks was to check the engine good and warm (give it an Italian tune up on the way to the test) and dump a gallon of methol hydrate in the tank before the test. In Canada, methol hydrate is used as a winter fuel antifreeze - and therefore comes in gallon containers. Not sure if you can find it, but I know this has worked for me in the past.