Ok, I picked up a 2008 Chevy 1500 RCSB 5.3l Auto Flex about a month ago. I plugged in and found the ethanol content @24% and LT fuel trims approaching -20 on both banks which is way too high, I ran a few tanks of premium(91) through the truck and the content level did not change. To my knowledge Hptuners doesn't allow me to reset the Ethanol content so I used tech2 to reset to 3%. I then reset the LT trims and started logging. The fuel trims went right back to high negatives almost immediately. The 02 readings seem extremely sluggish to me and I'm hoping one of you fine folks can take a look at my log and give me some input.
2008ChevyTrucklogafterEreset.hpl