Tigerfill

Hi guys i looking into modding my sti v3 i already have/will have

full 3" decat
panel filter
VTA dump valve
Walbro 255
Presure reg
ECU in progress

whats the most i can get out of my current set up?

and what do you thing i would need to get to around 350 -390

i have 440 injectors and it has been suggested i get 550's but I am unsure which ones will fit my car

Also how would i adjust the boost for mapping etc is it electronic via boost solind if so would i have to get a 3 port?
or would i need something like a dawes device to replace my restricter pill

anything else which is a must

also if you have a link for a topic which is similar let me know!

thanks Phil