This is the only compound able to take the temps. Anything else has a low melting point.....so yea, like high-temp JB weld, it will still melt off. I've heard of people using Marine-Tex successfully (marine exhaust repairs) but the company says they can't guarantee anything for manifolds because of the extreme heat.
This is the only stuff I've seen that advertises such a high temperature.
It did reduce the sound of leak, I must say.
BTW header wrap will keep in the temperature of the header, which can make them crack faster. Many header companies void warranties if that stuff is put on.....
Sure, it will get under-hood temps down, but your header will be just as hot, maybe even hotter since it can't properly vent itself.