Borlas are fine. They're 304 stainless on the outside with stainless and ceramic wool packing. It'll last. (And even if it doesn't, they have a million-mile warrantee.
) Oh, and I should mention this is actually for an FB, but I figured you guys would have more information on turbo exhaust systems. I suppose I could get just the right RB muffler, but for that price I could buy three Borlas and have cash left over.
I really appreciate all the opinions. So, it sounds like I'll be using either aluminized mild steel or 409 stainless if I can find some cheap straight lengths. Either way it should last a while as long as the welds are good.