1988 Chevrolet Other Carburated 454 with low emissions

I just rebuilt the caburetor in my 1988 Itasca, and took it to emissions to be tested. It has dual air pumps, emissions compliant exhaust headers, and no catalytic converter (did not come with one from the factory). It passed the tests but the readings seem extremely low. On the idle test its HC reading was 61 ppm / the standard is 300 ppm, its CO reading was 2.42 ppm the standard is 4.00. The idle readings seemed very good. It was also load tested on the dyno, these are the readings that concern me HC 8 ppm / standard 300 ppm, CO reading 0.39 ppm / standard 3.00 ppm. Can this be caused by a lean condition? Can a carburated 7.4 liter engine with no catalytic converter really be putting out less emissions than a Prius? I do not want to damage the engine.