After 2 weeks of "way too lean" condition after putting on an aftermarket muffler, I finally drilled out the air mixture plug.  First things first, that made one hell of a difference.  I still need to increase the main and pilot jets, and thin out the spacer...but I am much happier with how she acts just by making the mixture richer.

Anyways...has anyone ever put a plug (not the original of course) back in to keep the screw clean?  Either way, if I try to find something, should the material make much difference?  I was thinking a small rubber plug.

I know...it's probably fine without a plug since I haven't seen anyone mention anything...

And if you think about it, carbs on vehicles have no covers for the screws, and there's a lot of stuff getting blown around under the hood on those things.