Reassuring to hear! I look forward to the injector flow data you have to substantiate your statement. Although I concede the data I have gathered thus far is preliminary, per the measurements I have received from the flow lab I work with the JNC1 port fuel injector system is capable of supporting ~390 horsepower @ the crank at a 90% duty cycle flowing ethanol-free gasoline. Add the increased volume/Btu of ethanol and that figure decreases, ~290 horsepower @ the crank with E85 (a simple calculation could well-approximate maximum horsepower when flowing E40, but it's safe to assume that this value falls somewhere between the two). I will receive a full characterization report soon. Video of some the characterization process attached, pretty cool stuff.
Referring to the graph I have attached, and assuming it is accurately scaled and not a simplified graphical representation of the fuel injection schema within the PGM-FI, we can see that the direct injection system does indeed do most of the heavy lifting. As such, it is possible that Mr. Key is correct in that we have not reached the limit of the factory fuel injectors. Once I have the direct injectors characterized we will have a much better idea of what kind of headroom the factory injectors have left. I'll have more data pertaining to the in vivo operation of the fuel injectors once my vehicle is back together and on the road/dyno. Port injection side fuel pump capacity will also be tested in the coming months.
I am unfamiliar with a balance/power ratio, but you are correct that with increasing ethanol content there is more potential for contact-material corrosion, some metals being much more susceptible than others. Seeing as that there are many vehicles on the road with full E85 tunes, I doubt that potential for fuel system corrosion is the driving force behind limiting the JNC1 to E40 at this time.