Need some help on chasing around the check engine light. I had the 6 injector go out in October on my 2015 5.3. Replaced and had random O2 sensor check engine codes. Replaced all spark plugs and spark plug wiring and codes did not return for 9 months (last week). High voltage again on O2 sensor but was running smooth. I changed all 4 oxygen sensors so that I could start fresh. Immediately started having misfires so called a mobile mechanic. He came out and put it on the scanner and was able to catch 4/8 misfiring simultaneously. After about 5 minutes on the scanner the engine self corrected and ran for about 15 minutes until misfires started happening again. This time the scanner was reading 3/7. I did an intake valve cleaner can and drove it for about 60 miles on the freeway, only misfiring during idle. I replaced all 8 ignition coils and still having random misfires. Did a computer reset through disconnecting the battery overnight and it ran for 30 minutes at idle with no misfires. Drove it for 5 minutes with no issues. It sat for an hour or so then I went to drive it and the misfiring returned. Has anyone experienced this before? My mechanic is out of town until the 18th so seeing if there is anything else I can do or help steer him towards when I drop the car off. Thanks in advance!