As it's been covered already, if you really want more power from your zed, unless you're forging the engine, best option is Vortech Supercharger on a standard 350z DE engine.
Complete kit with everything required to get over 400bhp out your zed is about £5600. You could save about £1.5k - £2k if you install it yourself in your own time. Mapping and license for UpRev is about £500 with Jez@H-Dev.
How long have you had the zed, how many miles have you done in it so far?