please answer the following
has it always been a problem or just only started occuring?
does it ever occur during acceleration?
when it does happen do you loose power (volts) too or does the engine just stall?
if you look at ETC, SENSOR SW CHECK when the problem occurs, what do you see?
i would say based on what you have described that its not tune related, it would be pretty hard to tune it like that
do all the lights go dim etc, have u got a battery guage, if so check it when the car has the problem
or even look at MONITOR, 1 CHANNEL, BATTVOLT and see what it does when the problem occurs
have u got the stock ecu?
put it in for 5 minutes and see if you can replicate the problem with it
if you can, then run stock ecu diag with consult and it should tell you straight away