Probably because of the increased air flow the stock injectors cannot handle it.
The FPR is to tune the larger injectors with the stand alone ECU I would think.

 

Since the increased airflow from the ITB's requires alot more fuel as well, ITB's force the injectors past 80% duty cycle. The stock fuel pressure regulator is mounted to the stock fuel rail, which can't be used on ITB's. You need to set the fuel pressure to a psi that puts your new injectors into a safe duty cycle.

 

Gotcha

 

Nate...what is your ave mpg now?

 

I think you could get away without the larger injectors, maybe just an increase in fuel pressure

last time I checked wildcardtrd wasn't putting out more power than a stock SC kit, and you can run those on stock injectors. No offense

 

22-25 city, 28-30 hwy.

 

The CTSC kit comes with an in tank Fuel Pump & Comptech FPR...the larger pump provides the additional flow needed while maintaining a safe duty cycle. The comptech fpr is kinda wierd...it works by pinching down on the return line.

You could run ITB's on a larger pump and an adjustable FPR, but the stock injectors also physically don't fit in any ITB kit I know of. The height of the injectors is too short, and the o-rings are nowhere near the right size. You could find o-rings to fit, and fabricate a bracket to get the stock injectors to work, but now you're just getting silly. It's cheaper and more reliable to just get new injectors.

 

Ah, the real reason for the larger injectors.

Very nice setup you have. By next spring I will have Hayward 50 mm ITB's with my turbo setup. Unfortunately, I suspect that the plenum will kill a lot of that wonderful sound.

 

^^^That will be a pretty trick setup!