OK, things seem to be getting a little confused.
Cast iron shouldn't be wrapped, it'll crack.
Yes, race cars wrap turbo manifolds, a 4WD isn't a race car.
If you want to coat a cast iron manifold, use HPC, Jet Hot, Swain Tech, etc paint/ceramic coatings. They don't retain near as much heat as the silica based wraps.
As Inc said, wrapping the exhaust system from the dump pipe to the t/case definitely reduces felt temps in the cabin on a Defender.
As stated in the other thread, mines been in place on a heavily tweaked 300Tdi 3" system for years, and the wrap is still fine.

