Can i use injectors larger than 720cc??
Injectors larger than 720s (stage 1.7/1.8) or the presets (stage 2) can be used but they aren't as "plug-n-play".
Never use an injector that flows less than the preset you are using. I.e. If you are using 550/680cc injectors, use the 550/550 preset and use the fuel correction map to lean the mixture. Using the 550/720 setting can cause a lean condition and may result in engine failure. Never use less than 720cc secondaries when running the stage 1.7 chip.

Injectors larger that 720cc are commonly used and can be used with any rtek7 upgrade. For stage 2, you can use the 720cc preset to partially compensate for the larger injectors and then you will need to use the fuel correction map to compensate the rest of the way. With stage 1.x chips, you will need to have a fuel controller like an afc to enable you to lean out the larger injectors.

Also note that having a large difference between the primary and secondary injector size is not recommended as they make tuning the secondary transition very hard to tune. It's always better to go with 4 slightly larger injectors, than small primary and very large secondary.