What parts would I need for a k04 upgrade from a k03s, I know that it won't increase performance dramatically but just wanted to know what I would need if I was to upgrade. 

i take it your car is a Vrs i think it would increase performance quite a lot, i think you'd need at least bigger injectors. possible uprated fuel pump and possible larger inter cooler then a custom not generic  remap   and whilst i was at it i would renew the coils and plugs 

Okay thanks