I finally got that messed up exhaust bolt taken care of. I bought some nuts for it, but didn’t end up needing them: for some reason, when I went to replace them, the entire post came out this time, instead of just the nut. I used one of the bolts I had bought before, and it worked perfectly.
Now my exhaust is quieter. I’m not sure why it is still somewhat noisy, but at least it’s better than before. At some point I’ll look at the rest of the boltage there and ensure everything is tight.
The tighter exhaust seems to have improved my performance somewhat as well. Now, when my cylinder misses, the performance impact is not quite as bad, though it definately still is a problem. I’m not sure why fixing the exhaust would have improved the performance like that; perhaps the lack of vibration helps somehow, or just makes me more willing to pump more gas into the engine.