The knock sensor does not report misfire. The knock sensor reports detonation.
Misfire is reported via the crankshaft position sensor.
I'm not saying that grounds are unimportant, but grounds are not the first thing that comes to mind when I hear of misfire and knock-sensor problems.
Still learning here
I'm coming from a Diesel background and there misfire is extremely uncommon, and very easy to diagnose - there is only fuel delivery.
Gas engines are so complex in comparison.
At this point I'm following troubleshooting steps from the GM manual. You probably have the experience to shortcut that structured document, but I do not (yet)
I've already did a full tune-up (, checked compression: got new Plugs, wires, cap, rotor, MPFI injectors, Intake Gaskets, O2 sensors, MAP-Sensor, Knock Sensor) in truck, it runs better, starts amazing, gets good fuel economy, even when it throws the codes and CEL is blinking - I feel nothing - purrs like a kitten and pulls strong. At this point I'm just assuming that computer is temperamental. And that might be down to the grounds.
Since I found two wrong grounds with the process, I'm going to correct those next weekend and see if it helps.