I have no personal experience with the lexus V8. I can give you some other things to think about.
Thottle position sensor, on Gms when the throttle is wide open it signals the computer to enter the clear flood mode.
The injectors are signaled to pulse by the computer. The computer can rely on different sources for input as when to fire the injectors. Cam position sensor, coils, ignition module. This can change depending on wether the engine is starting or running.
Like anything electrical, wire shorts and corroded connections.
Lastly some engines have a cold start injector with some sort of timing switch control.
Hope this helps. Try posting in the toyota section for more input. : Idea:
I have a 93 lexus ls 400 and am in need of some diagnostic information on the fuel injection system the vehicle has spark and also has fuel pump and fuel pressure but the fuel injectors are not firing yet if I spray carb cleaner into the air intake it will run but only untill the fuel is gone does anyone have any suggestions