I'll admit that I know nothing about 70's emissions equipment, so that's why I need some opinions. My 1979 Dode Colt failed emissions - it passed every test with flying colors - except for CO% at idle. CO% at speed was well within the boundaries though.
What could it be?

can you post all numbers and engine size?

long story short, high COs normally means you are rich,

It smells rich. But the hydrocarbon readings are low, so I was perplexed. I don't have the numbers with me unfortunately. These cars don't have a catalyst either, so I suppose I'll take a look at the carb and the air injection system and see what's amiss.

My guess is an EGR valve is sticking open at the wrong times, or its spring has failed letting it open too soon.