Since it's always being filled with outside air, I don't see any benefit of insulating it. The air inside it doesn't sit there and get heated, it gets ingested into the engine. It spends even less time in the air box when you're right hand is cranked all the way back, so any heating during its milliseconds trip through the box is less than negligible.
The airbox is not a reservoir that stores air for when you need it. The planet itself does that part. You want cooler air, ride in the winter.
As for icing down the intake manifold at the drag strip, keep in mind that such cooling only needs to last a few seconds. It will not affect something that drives the hills all day. Also keep in mind that we have no intake manifold to speak of. There are mere centimeters between the throttles and the valves.
Anybody actually monitored the intake air temp in an insulated vs. non-insulated air box?
Now, put an A/C compressor on the bike and the condensor in the intake path, and maybe you'll cool the intake air. Compressor load might offset your power gain, though. . . .
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