Surprise, I think what you should do is spend about twenty grand and swap in a fuel injected blown hemi and then move out of the state of Arizona, hell my brother lives in Idaho and their they all rip off all the smog equipment on their diesels and they can even carry loaded guns behind their seats there!
Oh come on, I'm just kidding!!!!!
Before you run off and do all the silly stuff that would be an absolute waste of money and time, try to solve that actual problem. High CO numbers are an indication that something is not right and this is not going to be solved by doing the silly fixes.
It sounds like you have already done many of the basics such as a tune up. I have been required to smog my MH each year over the past two. I have had to deal with CO too high at idle.
First, you should answer the question of whether you have the Federal model or the California model. If yours was originally sold in Oregon as was mine, you probably have the Federal model. It's too bad that the vin number doesn't state that. The Federal model only came with the air injection system and PCV valve. if there is no provision for an egr valve on the intake manifold, you most certainly have the Federal model. One way to tell is by the casting number on the drivers side of the Quadra-Jet carburetor, that is if it has the original or the proper replacement. You should see a number that starts with 1708. The sixth number if a 1 or 2 is Federal, if 3 or 4 it is California.
Absolutely don't add cats if it didn't come with them from the factory.
Also, absolutely do not disconnect your vacuum advance for the test! Make sure the mechanical advance and vacuum advance are functioning. Also make sure the vac.um advance is connected to the correct vacuum port. Understand the difference between non-ported and ported vacuum sources. Most distributors are connected to manifold or non-ported vacuum. This means the you have a vacuum at idle and none at full throttle. By all means remove your vacuum advance if you are drag racing your AS and have spent thousands of dollars utilizing and tuning such a system. Just joking geez!
Make sure you have no vacuum leaks and ALL vacuum lines are good and connected according to factory specs.
Do not run old fuel for your test. If that tank has been sitting around for a long time, take a nice long trip and fill up with a good brand of fuel before your test. Test with a fresh oil and filter change. Old oil will contain lots of HCs which can have an affect on the test.
You mentioned a popping in the exhaust under deceleration. If you have an air injection system, which you stated you do, this popping is almost always due to the air injection system not functioning as designed. I won't give you an unsolicited lecture on removing your air injection system...I only have one head and it has already been chopped off! There is a running joke about never buying a vehicle from Oregon because the smog equipment had been removed or disconnected. My parents lived in Oregon and so did DadsToy. My father had disconnected the air injection system by removing the belt and pulley. I spent about $70 for new pump, $10 for a pulley, two months figuring out that the pulley bolts were metric, over $300 on the diverter valve and maybe $60 on two new check valves. The original check valves had rusted out and so hot exhaust flowed the opposite direction which burned out the very expensive diverter valve and the pump itself. The vacuum line to the diverter valve was also disconnected and I almost went crazy trying to find a diagram as to where this vacuum line connected to the carburetor.
my shirk says I'm all ok now as long as I stay on my meds.
If I understand correctly and that is only about 50% of the time, the air pump diverter valve will divert the pumps air to the atmosphere during high vacuum such as deceleration. If you are popping at this point, I would say the air injection system is not functioning as required. Make such your exhaust manifolds or headers are tight...air getting in here with out an air injection system is usually the reason for popping as well.
Next you mentioned a rebuilt carb...I'm assuming a Quadra-jet. This would be the next thing to look at. It may be running to rich above idle (your load test). One typical reason here is the float is improperly adjusted.
Anyway, you first need to answer the question about federal or California model. If you can find the casting number on the Q-Jet, I can tell you if it is the correct one for 1984.