The wrap really does lower under hood temperatures, i don't believe some of the people replying here have every actually wrapped anything, you see it a lot on LSR cars because of the tight packaging and needing to keep heat out. With that being said, yes it does rust your pipes but sometimes you have to choose the lesser of two evils. I wrapped my fenderwell headers on the Henry J and after getting chastised here on the forum I removed it and immediately noticed a heat difference and I dropped a mile per hour at the track. When I redid my bike in 2014 I went back with the wrap and my pipes are still solid and not rotting off like was said it would do. I bought some used stainless fat fender headers last year, the craigslist photos showed nice shiny headers, when I got there they were wrapped, guy said he used them to break the motor in and a handful of start ups. I bought them and brought them home, I didn't care for his hose clamps holding the wrap on so I took it off, that shiny stainless was gone and a baked on rusty material pattern was left behind. I hit it with some 000 steel wool and a gray scotch brite pad and neither phased it, not sure the brand that he used or anything else like how cheap the stainless is but it definitely attacked the stainless. The Henry J headers, like I said there was a noticeable difference in heat and heat soak with it on then with it off.