To put it into perspective on my 07 at 17.5 PSI, stock turbo, intercooler, fuel system, Cobb TBE and SRI I was at about 220 AWHP. With my 20G, supporting mods, and 20 PSI almost 330 AWHP. Only 2 more PSI, but 110 HP?? Its the mods, the tune and the turbo. Your stock fuel system will not get you much past the 270 HP mark without maxing them out. Let alone your small IC. You need to upgrade those also. Changing out the IC might get you a little closer, but Im sure that the stock injectors will be maxed out.
"2007 WRX- PPG'd, 20G- Tim Bailey tuned
Stage 2 2005 WRX