Well first, is your header split for twin scroll, cuz if its not, just run a t4 non split flange, whats the point, thats somewhat the reason for the turbo to be spilt, Second if it is 2 - 2-1/2" max 16ga 321 stainless for each run into the split works good, But if your not running a split header, then, if your uppipe is 2-1/2" get a transition to 3" reduce from vibrant
works good, but is 304.
Add Bracing, Cuz when i use t4 split flanges, there on bigger frame turbos, and they weigh 40lb+ (GT4294r's GARRETT, not obx, jdm style ****)
Its not cheap to be cool!!