This doesn't have to be spark knock. Vibrations or struggling against the torque converter can easily create false knock and have that show up in a log. E85 isn't the god of fuel to rule over all knock retard events.
First you claim it's false knock. Then you claim it's detonation/preignition.
2001 GTP Drag Car - XPZ, Tischler heads, Upsidedown M90 IC'd, e85, Gen V, 2.3 w/ 5%OD
2005 F350 6.0 - studded, deleted, tuned
2001 GTP - cam, headers, nitrous, stock trans - 11.83 @ 116 <$2k in mods - sold