Even unported standard has achieved over 450hp.
Top effort on porting standard manifold & fitting best design elbow & exhaust is where money wants go.
If going tubular it needs be proper quality & design, runner length & diameter all important for proper worth while result & needs match your build criteria .
If you using a turbo that will fit in stock location & flange then stick with standard & port it, blueprint it to head ports & do a nice effort of heat wrapping it .
Equal length runners are not huge concern on turbos, gas velocity & free flow is important though .
Shiny parts look nice but without design data such as runner lengths, diameters, flow bench & dyno results most are nothing more than short term jewelery .
Stainless not a great material for turbo manifold, like woody mentioned steam pipe is pretty good, you can make some first class manifolds out of the pre formed steam pipe bends & it will last years & if ceramic coated look better too.