Yeah, that's not how you increase horsepower.
The ECU controls fueling from a 16x16 matrix. This matrix is specifically designed for use with your current injectors. If you were to switch out your injectors for bigger ones, you'd get a multitude of problems.
-Harder to start, due to fouling the sparkplugs with excessive fuel
-Excess fuel consumption
-Too rich in every load cell. It will idle high, it will sputter on acceleration. At best, the closed loop controls of the ECU might pull some fuel.
-Check engine light. When closed loop control (lambda-sensor) exceeds a certain % of fuel pulled, it will trigger a check engine light.
All in all, a bad situation.
If you want to squeeze out more horsepower from your engine, first, get a wideband sensor. After that, get a Nistune board, and start tuning your engine. This is going to cost money, but it's the best bang/buck solution. This scares alot of people on the forums, but it is the right way to do it. The learning curve is steep, but the reward at the top is worth it.