Ive currently got a S1 RST with the following parts fitted:

T3 hybrid stage 1 turbo
Pace double capacity intercooler
-31 actuator, roughly at 1bar.
Ported + Polished head
Kent cam (CVH 34 i think, but mightve been 32 or 36?)
Group A (i think) Head gasket.
Full stainless system.
K+N filter
Unknown ECU reputably from a 225bhp car. He did mention bayoo or bajoo but i cant be 100%.

What would i need to change to make considerably more power. Im looking in the 275bhp to 300bhp region. Is it a fair target or will it be mega money?

Would it need a new ECU altogether?
Can the standard injection system handle it?
Id need bigger injectors, how big?
Can the Turbo do the job?
Can i wind the boost up a bit instead?

I may fit a FMIC soon anyway with a double fan kit so that wouldnt be needed.

Sorry for the questions, but i dont really know much about these engines, im more used to good old fashioned carbs. Cheers.