I have been running an E30 mix for over a year and a half and probably about 25,000 miles and I had LPFP issues with the regular JB4 with the 18ohm resistors with that mix. When I switched over to the JB4 15ohm board for some reason I could run more E85. Now, with the JB4 G5 ISO, I can run up to about a 60% mix without ANY codes. I think with just a basic tune an E30 mix is ok. If your trying to get big numbers and have the latest and greatest tune like the JB4 G5 ISO with the BMS flash or the Proceed Rev3 with the flex fuel system and Shiv's flash then you can def run an E40 or more mix no problem on the stock fuel system from my experience and from what I have read. I have a buddy with the Proceed Rev3 with flex fuel and flash running 100% E85 and he isnt having any problems as of yet. But its only been about 3 weeks or so. We will see how long it will hold up in a couple months down the road.
[size="2"]Crimson Red E92 335i M-sport 6-speed with MHD custom stage 2+ flash only , 40% E85/93 mix,+ HRE P40S wheels, KW Clubsport, M3 sways,+BMW performance CF Mirrors, BMW Performance CF deck lid spoiler,+ CF interior trim, p3 vent boost gauge,+ LUX angel eyes (11.73@124mph on street tires)