Probably the cams for sure

 

it's going be nearly impossible with the stock turbo, unless you go alky, meth, E85, or race gas. Do you want 400 at the wheels or crank? Just to give you an idea. I have a 20G-LT on 91 octane, stock injectors with 320awhp on the Mustang dyno. So good luck! Here are the list of my mods from a local forum for reference.
http://www.evomn.net/forums/garage.p...vehicle&CID=43

 

if you put cams do you need to tune at the same time? or can you just drive?

 

To benefit from the cams you need to have it retuned. After I had my cams in my old EVO installed, I had the car tuned the next weekend. I drove the car, but I wasn't hammering on it.