I am a fleet mechanic and have to deal with a small fleet of 2010 Impalas that must run E85. They constantly revert back to low alcohol readings and run horrible/ set check engine lights. Has anyone changed the tunes on these pcm's to stay E85 or adjusted parameters that would help these cars keep the high alcohol learn that I tirelessly obtain by draining the tanks and forcing a learn mode refill. THANKS, Rodney