Adding larger fuel injectors won't increase power output unless the stock ones aren't able to supply enough fuel (i.e. the car is running lean and the injectors' duty cycle is maxed out). Given that, in stock form, the car runs rich, adding larger injectors really won't help. Also, if you watch the AFRs, they tend to drift to around 12.0-12.5, which is rich for an NA car. I've disco'd the battery, resetting the ECU, in order to watch the AFR's adjust over time. Immediately after begin reconnected, the car ran extremely rich (~11.0-11.5) and slowly adjusted to 12-12.5. I'm willing to bet that if you add new injectors and don't tune them at all, initially the car will run extremely rich (< 11.0AFR) and eventually the ECU will pull fuel so that the AFRs are adjusted back to 12.0-12.5.