have you considered the likes of 5zigen, i have one very good header or if the budget is higher mayb a mugen or toda.The thing is your goina want proved gains would be worth looking into this rmf header to see if there is actually graphs to prove.At the time i was going to buy a manifold i was going to get a dc sports but was told they dont have proved gains but then found a new 5zigen off a guy baz ctr on here which does so i bought it. But im no expert im sure someone will no more about this than me just thought id try help out