Need help with emission sniff test

[ROWSC]

I have a 1979 R.o.W. SC with a modified short-stroke 3.2 (PMOs, Weber cam, dual plugs...). I have an EPA exemption from the visual inspection so "all" I need to do is pass the sniff test once and I am good for as long as I live in Colorado. I am still breaking in the motor so I don't have any baseline numbers, but the shop said the CO% was around 4% when they adjusted the carbs and it needs to be below 2%. What if I installed a later model exhaust system with a catalytic converter? What would this buy me for emissions? The exhaust on it how is a pair of custom GHL heat exchangers and a dual-in, dual-out Monte muffler. These would go back on after the test.

Thanks,

Rich