I don't know how far the PCM can swing to adjust the tune for closed loop, part throttle tune, I don't think SCT can tweak anything but timing tables when it goes into closed loop, but I'll have to run that by the guy I use to write the programs.

but my modified 5.9 that makes 285rwhp cruises at 14.7 AFR in closed loop mode, and is running stock injectors, pump, computer, etc. the only thing adjusted there is the program on the PCM via SCT.