I am looking at getting a Simtek ecu fitted to my sti v3, I have decat, hks filter with zerosport induction, uprated clutch.

Car has vf23 as standard and 440cc injectors, I am fitting a walbro fuel pump but am aware that with the above I will be looking to get around 330 bhp. What is the limiting factor that restricts power to this level and what should I be looking to upgrade to, turbo/injectors/fuel regulator ?

Also is the sti v3 box stronger than the uk/wrx box. eg will it handle 350+ bhp?