There is a lot I don't know about motors but -

1. heat insulation for the headers gets more heat energy to the turbo.
2. on a N/A motor, by retaining heat in the headers the only effect will be poorer scavaging on exhaust cycles. So, what is a good mod for a turbo motor will cause a drop in power on a non-turbo motor.

Heat wrapping - I have seen reliable sources, ie people on this forum, state that the metal inside the wrapping can corrode and disappear leaving just the wrap.