TJ if you look at the comments on that video he used the wrong baseline… he said the stock one had 355 i think… so a 45 hp gain seems a lil high but nothing out of ordinary. most of the ones i have seen are doing 366 stock…
they have 2.5 duals on them stock i believe… so headers and some muffla’s with stock true duals on the ls3 should be pretty nice… the l99’s exhaust are way more constricted to keep the tone of the cyl deactivation down.