Going to replace all 4 heater sensors, not sure where the knock sensors are or what they do and how to fix, and the knock sensor 2 low circuit input (Bank 2)what and where is that and what is the fix, any help is appreciated I have a helper that is kin to Google, Sir, Alexa and whatever the other names are and not getting anywhere

CEL flashes on decel or trying to maintain speed going downhill at 65mph+. Code reader says evap system issue

The light comes on at 75 mpd, code P0300, changed wires, air filter, added fuel injector cleaner(twice), runs fine, no change in performance. What else should I do? or not worry about it?