from team zr1...
more info can be found on this page
http://teamzr1.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=10&t=000028

Use the 80% max duty cycle rule for injectors.
(Inj. Size lb/hr) x (Duty Cycle) / .50 = HP rating per injector 

------------------

a stock injector of 26 lbs/hr would only handle :
  Ability of Your Injectors IF 26 lb/min using a BSFC of .50
   80% Duty Cycle = 333 FWHP 
   100% Duty Cycle = 416 FWHP 
   (283 and 354 RWHP)

---

(stock 1998 injector) 28.4 lbs/hr equals :
  80% duty cycle = 363.52 FWHP  
  100% duty cycle = 454.4 FWHP 
   (45.44 Crank HP x 8 = 363.52)
   (56.8 Crank HP x 8 = 454.4)

---

if you went with Ford SVO 30# which are 36 lbs/hr using 58 lb fuel rail pressure
that works out as :
  Ability of Your Injectors IF 36 lb/min using a BSFC of .50
   80% Duty Cycle = 461 FWHP
   100% Duty Cycle = 576 FWHP 
   (392 and 490 RWHP)

---

Using 38s :
 Ability of Your Injectors IF 38 lb/min using a BSFC of .50
   80% Duty Cycle = 486 FWHP
   100% Duty Cycle = 608 FWHP
   (413 and 517 RWHP)

---

and 42s :
 Ability of Your Injectors IF 42 lb/min using a BSFC of .50
   80% Duty Cycle = 538 FWHP
   100% Duty Cycle = 672 FWHP
   (457 and 571 RWHP)

          
------------------------------------
posted on ls1.com.....

First of all, all injectors are rated at 43.5 psi. Therefore the 30lb 
injectors flow 30# at that pressure. The LS1 runs a high fuel pressure 
of 58-61 psi. This effectively makes these injectors flow 36#. This is 
enough fuel for hp at the flywheel of over 650. 28lbers are not far 
off that #, but if you continue to mod add ford 30lbers...

The reason for bigger injectors with this setup is as follows;

1) When tuning with LS1 Edit the stock injectors are harder to control 
between 5800-6500 rpms. This is where fuel calibration is most important. 
Also the injectors are running damn close to what is called "static". 
This is when the injectors is pulsing between 85-95% of it's duty cycle. 
This puts an injector on it's edge. If an injector goes "static" it can 
either stick and wash the motor down or you could cause the injector to 
fail. When using the larger injector you can tone it down where peak 
torque exists and really crank it up at peak HP and still only have 
the injectors running between 75-85 %.
Thanks to Redline Motorsports for the info.