I changed some vacuum hoses that were a bit cracked. It didn't seem to do anything, but it's good to have it replaced anyway. I've checked every connection I could find to the airflow sensor and they appear to be fine. Although, there is one that I can't seem to reach without taking the air sensor and fuel distributor off. I will try to check it if the other possibilities don't pan out.
However, the most interesting thing happened today. I found a couple more hoses that were cracked, one of which connected to what I'm pretty sure is the cold start injector. I took it off to inspect how badly it was cracked and found that the metal connector to the hose on the cold start injector was almost completely plugged with hard black stuff. I took the connector off, cleaned it out, and reattached everything. To my great joy, this is the first time I've noticed any difference in how it ran. I started it and it idled higher than normal - slightly above 1000 RPM, instead of 900 like before. I waited for about 40 seconds and it seemed to be steady, which is longer that it has ever lasted without starting to die. Then I revved it to get the temperature up. When I quickly took my foot off it bogged down almost to the point of dying, and it went up and down for a few seconds until it resumed idling steady. I revved it again and this time took my foot off gradually - it didn't bog and resumed idling well. Then I tried revving again, and it wouldn't idle steady again, regardless of if I released the peddle gradually or not.
So, I'm going to try two things tomorrow: I'm going to replace the cracked hoses, and I'm going to do some diagnostic tests that are outlined in the service manual to test the cold start injector and the thermal timer. I want to see that:
A: It is spraying correctly, and
B: The thermal timer shuts it off. The manual says it should spray for no longer than 12 seconds.
The two service manuals I have are frustratingly vague in some areas. There is a mysterious thing that is connected to the vacuum hoses that I suspect is a vacuum booster - however, there is not a single mention of it in both manuals that I can find. If it is a vacuum booster, would checking the gasket for cracks be a good idea? I attached a picture of it.