Hi Paul,
Don't forget that power graph we gave you is at the wheels, not the flywheel.
You can drive it over 5k-rpm, just not with hard boost.

Everyone else:
803s and T34 when the entire installation is brand new, will do the job.
The problem is, so many things affect how much fuel you can get from an injector that its just a setup that actually worsens with time.

Fuel pump wiring
Self explanatory I am sure.. we regularly see this under 11volts nowadays.

Management harness
This gets complex and the obvious sensor issues aside, its ability to switch an injector correctly and accurately for high fuel flow diminishes as it gets older and more resistive.

ECU voltage
This is absolutely critical as it is in charge of opening and closing the injectors, and that requires significant current for the low impedance peak and hold injectors this old technology uses. Its very easy to lose around 6 thousandths of a second through lack of ECU current and degraded injector harness wiring, and that's without the loss of flow you can experience if the fuel pump harness is running the pump voltage low.

That figure I just mentioned may not sound much... 6 THOUSANDTHS of one second? But consider this... an 803 opening long enough to supply enough fuel for 350 bhp is open for about 20ms per injection event. If we were to intentionally only open it for 14ms the engine will run in the high 13:1s and melt a piston.

This is why we err towards bigger injectors on older hardware as the opening times are much lower and we have more margin to correct for the fuelling problem in the map if one exists. We cant run much higher than 20ms effectively on a YB as we are of course limited by the induction stroke time base amongst other things, and the harder we rev it, the less time we have - and thats where bigger injectors come in.