You have an MY01 WRX, go to a workshop and get a re-tune of the stock
ECU (RT / MMS for ECUTek, ASG for Verso)
For instance, a Verso retune for $990 will give you more boost with a correct tune so you will not blow your engine to kingdom cum. (Blow, cum, lols)
Upping boost alone is BAD, do it right and reap the rewards.