IFR and O2 sensor readings

Just wondering if anyone can explain how injector flow rate changes the o2 sensor readings and the tune for that matter ? ive been dialing in these mystery ebay Bosch 0280155737 injectors and finally making some progress making them run. it seems the happy spot for these injectors with a return style system is 40#.
If I go up to 41# I get massive KR and the VE keeps asking for more fuel, if I go down to 38# it keeps pulling fuel out of the VE. With the IFR at 38 the o2 sensors stay high all the time and rarely switch. if they are at 40# the O2s switch normally and the VE seems to stay stable.
these injectors are rated at 36# at 43.5# of fuel pressure, this vehicle has 58lbs with a FPR at the rail. Using 2002 Tahoe flex fuel 33# injector voltage offsets don't know if that's a mistake or not. Both log files are the same tune just different IFR settings.