I don't have a wideband yet, but very recently my LTFT's were bouncing at or near 16.4 and I got a P0170 (Bank 1 too lean). This started almost immediately after my last fill up. I'm running E85 on a stock tune with 42# injectors. First two tanks went through fine. LTFT's consistently around 10. Then all the sudden, boom. I'm lean.

Did they recently switch to winter blend? Shouldn't that have happened a while ago? Could that cause what we're seeing?