Yes you can, I believe 15.5V is 90% and you can set it to 95% max(according to some gm text)ya I was going to ask you if the hp tuners let you set it for like 14.5+ all the time like (min 14.5-15.5 max or no max)
my mechman seems to hang around 14.2 a lot with the ac on since it stays on here 24/7 from april until nov so it's one fix for me lol
here is a screenshot of the options available to me..
items in green I have deviated from stock. I lowered max voltage, and upped the rest. No idea what the fuel system minimum voltage map is for, didn't touch it.. or half the other settings for that matter!
DC max was 90%, DC min was 36% and the last two diag voltages I upped by 1 volt. (values shown are my modified settings)