these are made in taiwan or china in a mass production facility. So to ask for a few special aplications manifolds may not work. If they would see selling 100plus, then there may be hope. Just my 2 cents.
I would rather make a weld el mild steel manifold with schedule 40 bends and just mig the thing. this is along the lines of a log manifold but I would joint cyl's 1-4 and 2-3 then y the two branches at the turbo flange. this is how Lotus pipes there 400hp GT3 esprite. I would guess what works for them will work for me. They dont use weld els though, thought I would clearify that point.
Although I did bring up the use of the M5x turbo manifold, my one concern would be the weight of the turbo bouncing around on this manifold. This is why I would use the schedule 40 weld els. the mild steel would not expand as much as the SS and it would have a better chance of supporting the weight of the turbo.
Poll