This bigger A/R SS turbine housing reduces back pressure and heat normally seen within original OE A/R turbine housing, less restriction, and increases more flow (=more power)

IS38 turbine housing

IS38 06K145722H turbocharger stainless steel turbine housing

Ceramic shell building and drying for stainless steel turbine housing

Machining v-band stainless steel turbine housing's install flange

Machining stainless steel v-band turbine housing