wastegate size

im running a t3 with .42/.48. i wanna have between 6-9 psi. I don know what size waste gate to get. I know what spring rate just do know what mm. 35mm,38mm,40mm,50mm.I dont want to get the wrong one…please help.

a tial 38mm will be perfect, they don’t make the 35mm anymore. the 38mm is good to ~500whp.