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Rust proof coatings before wrapping/insulating will help prevent the rust from forming.

Hotter exhaust piping should keep the exhaust gasses from cooling as much (part of the point of header wrap), which should make exhaust flow stronger, higher velocity, increasing scavenging. It's theory, not practice, that covering the entire exhaust will achieve bigger gains in this department.

At the very least, it will stop parts of the exhaust from cooling as much while the engine is off or at low load, where there is less heat energy in the exhaust.

Faster exhaust heating times will also mean that less moisture gets trapped in the exhaust from short-distance operation.