I'll be using the JB4 "Autotune Map" which can raise boost to as much as 16 psi.
From what I've seen 49% of pure E85 is the safety threshold for the n54 cars. A 35-65 ratio is considered the average safe ratio.
I'm not sure technically how effective it is in one area or another but it does tend to do 2 things consistently; increase power and decrease mpg.
I'm shooting for roughly a 20-80 ratio on first attempt just to see if any issues pop up. If everything goes well I'll try the 35-65 ratio and get a dyno run of that.