****PSA****
If your truck is sensing knock randomly and pulling a ton of timing seemingly for no reason check those knock sensors even if they are only a couple years old and you aren't getting a code.
Been struggling to get my buddies 408 denali tuned right, it kept sensing knock at idle, part throttle, and even WOT but not all the time probably 60%. Had it down to 8*at WOT and nearly none at idle yet it was commanding into the negatives because it kept sensing knock. We changed plugs, different fuel, octane booster, 1,000 different things in the tune, and even checked everywhere for some sort of mechanical interference like headers on the frame. Finally we pulled the intake and check the sensors again which he reused from the old engine since they appeared to be in good condition.
Turns out one had corrosion on the pin, replaced them both with AC Delcos and now shes barking with 22* just for starters and no knock to be found.
I'm shocked the ecu never threw a code. I nearly burned the truck to the ground because I feared a poltergeist had possessed it.