Accel aftermarket 4 hole injectors claim 150 um droplet size. While the denso 12 holers claim 50 um. Anything under 70 um is considered fog. I can't say whether denso will give much fe improvement. At 5x the cost it seems like a poor return. Maybe gm figured that was the best compromise for fe and emissions. Def won't see any gains above 3500 rpm.
The parameter in the ecu you want is 'target afr'. Best lean torque is around 16.1:1. And also worst emissions. Upload the original bin file before gettin e-tested. You can do 18:1, and With a strong ignition system, 24:1 is possible.
Fuel injector offset IS a big deal if you increase injector size or change cams. Letting the ecu find the afr is ghetto
