he said not to say downpipe. Seeing as he put Yorba Linda as his location and that’s California I would recommend against a manifold( pricey for the amount of possible gain) and downpipe( effectively nothing gained below 375 hp besides sound) As those just shout I am not a legal setup.
Honestly for good numbers he has what he needs unless he is A power hungry and B. likes greasing palms and or swapping parts every few years for the sake of smog.