I have been looking at Pypes shorty headers made with 304 polished stainless. 300 series stainless is not supposed to rust. It may discolor with heat, but not rust. Headers made with 409 stainless will rust unless you get them ceramic coated and even then if you chip the ceramic when installing or fitting it will rust there. I was told to buy the headers uncoated for fitting, them have them ceramic coated before the actual installation.