Fuel jets are usually replaceable/ removable. Air jets are usually drilled into the carb body. Making a large hole smaller would be an interesting challenge in that the material is difficult, at best to weld and add metal, particularly inside a small tube.
Further, adding pods generally reduces the vacuum or "pull" on the fuel jets. Getting them to flow as before by widening has a greater effect than narrowing the air jet.
Also, the main air jet usually feeds both the main and throttle valve jets. These two fuel suppliers may need to be adjusted separately to address mixture differences at certain throttle settings.
It may be interesting to note, that in the Honda shop manual pictures of the cb550 K3's PD carbs, they show screw in air jets. I expect the pictures were taken of engineering development carbs where they fine tuned these carbs for optimum settings, then specified a drill size for production models.
Cheers,
