Only the parts CD can help with comparing the injectors - and I don`t have one at work I`m afraid.
Could be that your poor 8v is just running out of puff-power at high revs. After all, 16v only really become an advantage at medium to high revs due to the increased gas-flow possible (at low revs 16v generally have too much flow). Cam variation timing helps a lot with these characteristics but it may still be that you are seeming to loose some power at very high revs because the engine just cant get rid of the gas quickly enough - a problem made worse by a car that is very efficient at getting the cas in!
It could also be that the ECU mapping wont allow the amount of fuel you need now your engine is more efficient - I beleive they do have maximum allowed flow rates.
Experimentation would seem to be the key!
All of this could be horse-sh*t of course. I just feel the need to type today.
from what you're saying, the injectors on my car are the same as an old Volvo 3.0 V6 engine. I would assume then that my injectors could supply much more fuel (if they can fuel a tank engine) and all is governed by (as Chris says) the ECU mapping etc.
Ah well, maybe take a trip to the scrappies and pilfer a few injectors from scrapped Ferrari's, TVR's etc wink
Since your injectors are happy to flow enough fuel for a 3.0 engine, I guess the way to get more fuel would be to increase the pressure - I'm not sure if the 8v's have an adjustable pressure regulator but if it doesn't something like an FSE power boost kind of does a similar job. If you make big changes in pressure or flow you will probably need a remap to retime the injectors to stop them putting too much fuel in, but small changes will probably be OK.
If you turn up the fuel pressure you will be able to get more fule into the engine - the ECU will use the same injector pulse widths, but with more pressure, more fuel will go in. However, do not go too mad - I think the standard regulator is 3 bar and will drop to 2.5 bar at idle - the vacuum hose from the regulator to the inlet manifold regulates the change.
I would try upping the pressure by about 0.5 bar using an FSE type valve - this will also react more quickly than the standard bosch unit and give a quicker jump in fuel pressure - should prevent the mix leaning off in sudden full throttle applications.
You can monitor your fuel mix in a crude method using the lambda probe and a home made device to read the voltages coming off the probe - I wil post this later when I find the circuit diagram.
In normal "cruise" running the ECU should sort the fueling to lambda by altering the pulse width on the injectors, however you will benefit from increased fueling on full throttle applications when the system comes out of closed loop control.