The muffler/exhaust on my buggy is currently open and free flowing. I have heard that packing the muffler can produce better torque and bottom end power. Is this accurate?

Re-packing a muffler only applies to a muffler that will accept packing material (usually fiberglass wrap). If the muffler has a removeable baffle, it will probably have bolts or rivets on the outside of the body that keep the core (baffle) in place. If that's what you have, remove the bolts and/or drill out the rivets, pull the core out, and you should see the remnants of the old packing wrapped around the core. You can use fiberglass insulation or muffler packing to re-wrap the baffle, then re-assemble.

If you just have a straight pipe with no muffler on the end, you'll need to purchase a muffler appropriate for the size of the engine and have it installed. There isn't any way to "pack" a straight pipe.

I built the muffler on my exhaust with an internal baffle and a removable end cap specifically for packing. I originally used fiberglass insulation, which I was told was an inexpensive packing. Sure was, but didn't last either. Since then, I have just left the muffler empty. I purchased some actual fiberglass packing this time, since I heard that packing may actually increase the torque. How much packing is typically installed? Is it to be packed tight or loosly?

I pack mine fairly tightly, and with enough that you have to compress it with your fingers as you slide the core back into the body. One you get the core wrapped, you can use duct tape or something similar to help hold it in place while you re-assemble.
If the core on yours doesn't slide out of the body, then just pack it in there tightly as best you can. The packing will condense and disintegrate with time, so tighter is better.

Yeah, fiberglass insulation isn't the best, but will work in a pinch.

Thanks for the info. After experimenting with the jetting and packing the muffler, the engine starts easier and revs up much faster. I still may have to bump the main jet up again when the weather warms up, but for now, this is the best it has ever run - although it sounds like a valve is tapping now, so I am going to have to check my clearances soon.

As for the muffler construction: I started with scraps from a converyor roller, which consisted of a 5" diameter steel pipe section and two converyor roller end caps. I welded the front end cap and bolted the rear, so that it can be removed, and installed a metal screen inside the rear end cap. I drilled numerous holes in the end section of the exhaust pipe, and capped the end, then welded the exhaust pipe into the front end cap leaving the drilled section exposed inside the muffler.

I've got a baffle tube in the center of it. The baffle tube is the section of drilled exhaust pipe that extends into the muffler. It sounds better with the packing. Still has a growl, but not so loud. (As it turns out, the previous loud noise level did not add any power.)

You could also use steel wool mixed in with the baffle wrap. Does blow out quite as bad.

Hey, my first post.

you could also use bronze wool instead of steel wool.cost more but it wont rust.

I have heard that the sheep that produce steel wool, have no known natural enemies... I am not sure of bronze wool.

yes they do......... its called rain!