they say that water will absorbe into the material and trap it next to the metal until until you turn your cars on, to me this dosnt make since as the water will evaporate as soon as it touchs your header.
ive had friends with header wrap on rsx-s race headers and took the wrap off only to reveal shinny clean metal, and my 7th gens header was wrapper no problems.
but your really only going to make 1-2hp extra not even measurable.
Former: 96 GT 5 speed(i/p/e)Fate-rear ended by mack truck00 GTS 6 speed(i/ Bored TB 63mm - 68.5mm w/ butterfly/ Ported IM/ IMG/ PFC/ Commander/ datalogit/ Ported & heat wrapped Header/ Decat/ UEGO/)193FWHP 14.2(1/4mi) @98mph, 2.12 60ft (just intake, unbolted Exhaust, and gutted)Fate-side swipped by 18 wheeler at 75mph.Next: maybe an elise
A) chrome coatings are thin, and can easily be worn through by the wear produced by the header wrap. Even if it's wrapped so perfectly the engine vibrations do not disturb it, you cannot avoid the metal expansion/contraction
B) Water may evaporate as soon as it touches your manifold or header when the car is at temp, but when the temps go down, the wrap does a great job of holding water in. Now you've got a damp cloth tightly wrapped around ferrous metal -- rust is a distinct probability.
C) Depends on the material. Some headers are made out of stainless, and therefore won't rust. The rigidity of stainless issues also mean they often benefit from the more gradual cooling produced by the wrap.
I say just leave it unwrapped
1999 Celica GT
Thanks for all of the replies.