I would start with programming and a tranny upgrade first. With bigger injectors, you might even need to run an aftermarket turbo or twins. From what I have read, the stock injectors are good for quite a bit of power. If it ain't broke, don't try and fix it. You are looking at quite a list of upgrades to make sure that you can use the extra fuel and power.
i would do the injecters as on of my last upgrades,with the stock injecters you are good up to roughly 490rwhp and any thing past that you will need a lift pump and bigger fuel rail and when you have the injecters to there max you can still support 550rwhp to 600rwhp and not run out of fuel..i would say a bigger tranny for your first upgrade and then a big hp tune,or a 90hp tune with the stock tranny..