hmm thats odd

from the docs
"Battery Voltage Correction (ms/V) (BatFac) is the number of milliseconds that MS2-Extra (or MicroSquirt Running MS2-Extra) adds to each fuel injection pulse to compensate for the slower opening of the injectors with lower supply voltages. Generally 0.10 ms/V or 0.2 ms/V is about right. "

my voltages are super steady at 13.2-13.5 other than the random spike once in a while

i lowered the correction to 0.050 and its not noticeable anymore, whats your setting and what injectors do you have, remember with bigger injectors a small pulse width makes a big difference.