I would run map 5 starting out with about 25-30% E85. Do some datalogs and check out your fuel trims after you do a couple of WOT pulls. If the trims are low, add more E85. I wouldn't jump into too much E85 and then find out the fuel can't keep up causing issues. So 25% E85, a couple of WOT pulls for autotune, datalog, see what others think, then adjust E85 accordingly.
Current: 1997 E36 M3, 2015 F80 M3
Past: 2011 E92 M3, 2011 E92 335is, 2008 E90 M3, 2007 E92 335i, 1995 E36 M3