I highly doubt aftermarket injector builders can do a better job than the factory suppliers.Aftermarket injector builders do alot of R&D with alot of dyno time. They get a better spray pattern from stagering spray angles and adding more holes to the tip.
There's no comparing the R&D budget of a small aftermarket company with engine manufacturers and their OEM supplier.
Engine makers compete on BSFC. If there was a fuel consumption improvement to have then they would have it.