PSI does not equal power (really wish people would learn this).
Mass Flow equals power.
That takes into account CFM and AIT's. High CFM + High AIT = crappy Mass Flow vs lower AIT.
AIT's (at moderate pressures) will reflect the efficiency of the turbo. Low efficiency and it'll heat the air too much. That means you need a larger intercooler to chill the air; which lowers the response/spool.
You're looking for a turbo that flows around 400 CFM @ ~80%.
There's good reason a lot of the TC guys don't use the stock turbo (myself included).