Good evening, i have a stock 02 tahoe 4x4 5.3 flex fuel that i have been trying to track down why i keep getting lots of knock retard when cruising or under a slight load, truck has around 260k on it, i replaced the knock sensors with oe sensors and installed a new harness as well (had codes for them), intake gaskets while i was there of course, and spark plugs with new wires. under wot conditions everything seems to be fine, i have done some tweaking on the power enrichment and torque management things in the tune as well as e fans. i run 87 octane most of the time, i have run 93 octane to see if it helps but it still doesn't change things, i just filled up with e85 this last tank and i did a log tonight and was surprised to see a lot more kr than with regular gas. another thing i have noticed is the terrible fuel economy, 12-13 mpg hand calculated on 87, i know these aren't honda civics and don't really care about mpg but i was expecting at least around 15-16 ish mpg. I'm thinking this knock retard issue could be why its so low. I'm attaching my e85 log file, maybe someone can help me out and point me in the correct direction, thanks!