Thank you for adding to the information posted.
Alpina, and other German tuners did indeed build stroker motors using the stock injectors, but from what I understand all changed the fuel regulator, increasing the fuel supply.
While admittedly my personal motor had likely tired injectors during my dyno session, they did CLEARLY move into "wide-open" when combined with software changes (Mark D'Sylva). With the stock chip, the AFR ratio was almost perfectly stoich through the RPM range.
You seem to be a knowledgeable person, therefore I'm sure you must have come across the simple mathematic formulae used to calculate possible power from a fuel injector. Using these, at 80% of the injector's duty cycle (the highest use generally recommended) a stock M20 injector can only make ~140hp. Using that number and calculating further, one will find that BMW is actually running the stock injectors at 96% of their duty cycle, in a bone stock M20B25. A 14.6lb/hr injector combined with the stock 3.0 bar regulator can only physcially make 175hp. This is simple physics, it's impossible to argue with.
I hope this is sufficient proof for you that stock M20 injectors are too small to add any sort of modifications to the motor and actually gain power.