Header wrap is a major NO NO on a street car. It will cause your pipes to rust out quickly. Get your headers ceramic coated. Yes, it's expensive. Yes, it's worth every penny. I had my headers done in CERAMAKROME, and ten years later they still look great. No extra insulation under the hood, I can put my hand close to them with the car running.
I gotta say that the wraps work too, but the rust potential mentioned above is (as I understand it) really only going to be a problem if you drive your car in the rain. The wrap can hold the water against the thin header piping long after the motor is turned off.