Injectors don't make power as such, they supplement it. If your stockers weren't at their limit, and limiting the amount of boost you can run (they wouldn't have been at 1bar) then you'll make NO more power from bigger ones.
Before the tune i reckon 210-230rwkw depending on a few factors.
Tuned you could make another 20, depending on how aggressive the IGN and AFR's are set (down to the experience of the tuner) As mentioned, its the low down response / tourqe (hence; fuel economy) that you'll notice more so then a top end. power figure.
When your leaking fuel from the injector area, clean away the stains with carby cleaner and look real closely. Often they leak from the small indent in the plastic body. Remove, clean surface and fill with araldite. Replace o-rings and insulators (as even if they weren't leaking to begin with, they could now after they've been removed and reinstalled, specially if they are the original 20yr old ones.
Sard 700's cost me about $110 each, 2 years ago. Perfectrun.com.au are hocking Nismo 550's for $125each atm. They take 20mins to install.
The above is the process I would (and have) gone through. You can do it all yourself with basic hand tools. If you do purchase new injectors, simply set the injector correction in the PFC and drive the car to your tuner.
GL