CAn someone explain to me what this is

 

Its a material designed to reduce the heat that came through the header. It was good back in the old days before coatings but is now obsolete. It can retain moisture and cause your headers to rust. Its better to spend the extra money on some coated headers.

 

Ah thank you

 

Doesnt it also hold heat in to keep exhaust velocity up (good), with the down side being over heated and eventually warped, damaged headers?

 

all the pro turbo guys i have seen wrap their headers - it might by you 1-5 hp - and cooler engine temps... its not going to damage anything!

 

not so sure. check out this link, it explains the damage header wrap can cause. Ive also read warranty statements from a couple manufacturers and they say the same...

header wrap

 

Wrong it will destroy your headers. It makes your headers to hot to the point where they fall apart. They will also void any type of warranty on headers.