Re: OT - Emissions question
This I know, having had my CA.smog license since 1978!
As you may already know HC(hydrocarbons)in the exhaust is raw unburned fuel; CO(carbon monoxide) is a byproduct of combustion; and NOX(nitrusoxides,laughing gas) is a product of the temp. involved in combustion.
now on to your blem; make sure you have a cleeaann! air filter,(not a fram, cause although they filter great, they are very restrictive(imho).
fresh premium in the tank,
and drive the old girl hard for a few miles, change the oil
make sure the carb is clean,
and that the diverter valve is working. and make sure the catalytic converter doesn't cool off when tested , the car must be hot!