Yeah Aluminum won't work for turbo manifolds. I'll prototype in it cause its easier to work with but thats it. I'm thinking about running iron at home on a larger scale but its a hell of a lot of work.
FWIW, I have a $100 chinese welder, fitted with a $15 sheath from a much more expensive welder, it gets the job done
I did my entire turbo-back exhaust including my active exhaust trickery, flanges to seperate sections, and flexpipe for around $140 in parts
Wont make a turbo manifold (or will it? muahahaa) but it does very well for basic exhaust work. Definately something to look into if you want your stuff just right on your car, only way to do it