Headers?

Anyone ever compared the Schumacher headers to the high po exhaust manifolds? I ask because they’re small tube for figment and I’ve heard 475 hp is all. But someone on here got over 500 with just manifolds. He actually wrote a book. His name evades me now... I’d like to know before I spend the money. Thanks
Just for info my car makes 500HP with Schumacher headers. And ran best of 11.37s.