you have to take the manifold out mate so it is quite a thing to do so i dont know why you thought that

we are building a track car at our workshop and when rebuilding the engine we wrapped it as it helps efficiency for both the exhaust and the engine itself due to the proximity of the manifold to the other parts of the engine

but i mean unless you are having a new manifold fitted there is no point doing it as you will have to take the manifold out, wrap it, pin it in place and then refit it.