What is the material of the OEM exhaust gaskets? Is it a metal base? Layered metal base? Reusable? The reason I ask is that I just got my long-tube headers and the gaskets that came with them are just regular cheap paper-based flexble gaskets. I only want to go through this once and don't want to have to deal with either of the exhaust gaskets blowing out, cracking, or leaking.