CHEVY express code PO300 with 4 ignition coils NOT firing

[@rellmonger7935]

Kool, I hope I don't have this problem. I started having a po300 code when I was on my way home yesterday. Mine is 05 Chevy Express 3500 with the 6.0. I had it 3yrs & had a misfire when I bought it 2019. I replaced with best plugs, wires & coil packs. I didn't want to do it again. So I'm going to just trace the bad part(s). It's my lawn care van. Only drives in summer.

[@sakocat]

could you have fixed this with a new wire harness