Bronx my tuner said something about keeping heat to the rear housing via smaller exhaust which somehow let's it spool up quicker (can't remember all of what he said,he did say 4" let's put more exhaust gasses and shows in top end.
It is 3litre rb30 bottom end not sure how much exact displacement is.
Looking to run around 30psi
Rev limit will only be 8k nothing too crazy.
Head has been heavily ported by 6boost
Also have a 6boost manifold so should flow decent,
And not to worried about the Law at this stage lol all power!.
Tailor made I've done a search and nothing quite as specific to my car specs.
Want to know if "I" should run a 4"