I take it you're having some 'fun' melting/destroying some stuff then.
Is the first one cermic coated? That's why it looks a bit like alloy? Doesn't say in the thread. Don't know if you could re weld one of them.
The bottom one looks like a "better" design wastegate route/path. I don't think it's just because it's shiney, but that bottom one is "sex"... Top one will probably do the job but looks a bit Massey Ferguson in comparison.
Would love to have a go at one of them
I guess the stamping on the bends is to do with it being schedule 20/40 then. Don't know if there's a comparable B.S.?
At the place where I did my apprenticeship we used to do mainly re-furb of heavy engineering stuff (coal mining machinery). I remember them doing a bit of Metal Spray for resurfacing some components, I once wondered if you could fab a manifold then metal something exotic over it/in it to improve it's heat resistance. Probably not worth it. Probably just wait for it to crack then make a new one.