Coils today rarely go bad but as mentioned move #5 and the sparkplug wire to a cylinder on the
other head and see if the misfires follows along with checking quality of the sparkplug
More common problems is with the DI (fuel injector) that may need a good cleaning or replacement
Check GM TSBs for your vehicle and see if anything related to misfires or DI that require software updates to PCM or replacement
Maybe try a good cleaner like
Seafoam, sold like Walmart, auto supply, etc
Put half of it in gas tank, other half either into intake manifold or into the oil
will run rough at first as it breaks up carbon buildup
You can also use GM's cleaner called Top Down, follow its instructions of use
but could even squirt some into sparkplug hole and let sit to breakup carbon
Sometimes there can be short time frame of multi misfires but not enough to trip a P0300 multi misfire DCT
Use a OBD-II scanner that allows you to monitor and/or record like the PIDs I show below,
all current and history of each cylinders will help pin down which one(s) are really start of the misfire
Assure good cleaning of carbon buildup as could be #5 is too dirty effecting valves working and closing correctly
Also check no issues with PCV or EVAP which could effect quality of air/fuel mass to cylinders and that injector is not clogged up