Just gonna leave this link here for a 1/2" -20 plug for anyone wondering what it takes to block the factory manifold smog pump ports.
Reading the posts in this thread it sounds like you can eliminate the AIR system when you replace your cat or put on headers or your pump dies.
The way this system works, there is a diverter valve between the pump and the manifolds. It sends oxygen to the exhaust manifold to help the catalytic converters start burning the excess fuel in the exhaust gas. Once the catalytic converter is heated up, it doesn't need the extra O2. So the diverter valve sends the air to the air cleaner. Maybe that increases the airflow and boosts performance or efficiency like a ram air system would, but I sort of doubt it.
AIR systems were only put in these trucks for a few years.
Anyhow, the newer honeycomb catalytic converters work better than the pellet ones the trucks with AIR came with. So, when you change your cat the AIR pump isn't needed. On the other hand, it probably isn't hurting anything either.
The only unanswered question I have is whether the diverter valve sends info to the ECM that will impact performance if it is removed. I sort of doubt that too, but it could be. I think when the signal from the 02 sensor is hot it tells the diverter to switch the flow from the exhaust to the intake.