Ok heres my suggestion from experience, tell your friend that kits are gay and worthless. DO it right go out buy part by part or even get a custom manifold built. If he is serious about power do it that way(part by part not a complete kit from somewhere,even the greddy kits are junk. Unless he just wants boost for the sound then go with a kit.
Just my 2cents hope it helps
KEEP IT SIMPLE,KEEP IT JDM