There's no cheap short cut way to do it, the workshop Nauli put forward will be recommending a dyno tune for your modifications and the extra boost you want to run. The standard BPV will be of no concern for a moderate power or boost increase, they may have issues after 20psi.

Given your expectations and lack of knowledge in this case, I wouldn't be worrying about a 12 second STi at this stage. It's never as cheap as you think.

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MY08 WRX 325hp/456nm/18psi E85