I'm just wondering, since my stock air cleaner is gone, (from Eyesore, 1978 Ea-71 4spd) The air injection system (or whatever it's called ) is drawing straight from the atmosphere.... When I plug this with my finger, I don't notice any difference in the motor (other than it is quiter without that gurgling sound)

Now, Is this something that is OK to plug off, or should I find some kind of filter for it?

sparkplugs, wrapped in duct tape, or... screwdriver ends, work great! plug the rubber hose parts. no big deal

According to the FSM, on the "Air Suction System" :

"The fresh air sucked is mainly used for oxidation of HC and CO in the exhaust passage and partly used for fuel combustion in the cylinder. "

So if the engine is using this system to supplement the carb in adding air to the combustion process, I'm assuming this should not be plugged. Is this a correct assumption? If so, can anyone reccomend a tiny filter that will mount to the silencer (the little silver canister at the top of the system)?

I would prefer to plug this, and remove the sound, but I want to be sure that won't be causing a rich condition in the chamber, or otherwise harm the motor.

With that in mind, is it OK to plug this system?

no, it puts air into your exhaust to help the catalytic converter work better. doesnt put air in the engine, puts air after the engine. ditch that crap