Ive wrapped manifolds with no issue, cast, mild steel, and stainless, wrapping with bracing too is wiser mind. As heat makes things softer, then it cracks without bracing.
My RX manifold is wrapped with DW heat wrap, and though only done about 1000 hard miles with it so far, it gets hotter than any SR will ever get.
Its swings and roundabouts, take your chances. But I walways do.