I'm sorry to ask about an issue that seems to have been discussed plenty already. There is a good How-To on 'Set CO Dwell', but after repeated readings, I'm still not clear if the air hose connection to the oil filler (from the air cleaner) should be plugged or not. In some places, it says 'plug'. In others, it says 'no'. The shop manual says to do it with the air cleaner installed and intact. Since the piping for that, which is internal to the air cleaner, is essentially open to the atmosphere, that would tell me if you do not have the air cleaner installed, that you should do the adjustment with the connection unplugged.

I can adjust either way, but then the engine nearly dies if I unplug (or plug) the connection.

Further, with air cleaner and all plumbing installed, doesn't this represent a significant source of unmetered air intake to the system?

Thanks