So I have a Z6 that I am bringing into the shop to have built up. I fully building the bottom end an am going to do a port polish and valves on the head. Where my questions lie is on what turbo I should be running. HP goal is 400+. I would like to keep lag to a minimum but I understand sometimes that cannot always be done. I've seen some builds with GT25 and GT30 turbos. To be honest I'm not sure too much what to look for in a turbo. I've been reading articles and information on turbos in general but I don't really have an idea of what I need. Ideas?