I have a p0301. Have changed the spark plugs and rotated coils to rule them out.

Check for vacuum leak and injector pulse. Plug wet when removed? If so, check compression. Seems we have quite a following here, hope you get it fixed!

I'd start looking at the injector or injector wire harness

When does the misfire occur? At idle? Under a load? Or all of the time? Is it constant or does it come and go?

Try the intake induction service, Per GM Bulletin.

Just rotating the coils will not show up a miss fire, as it will just move to another cylinder. Try disconnecting one coil at a time when engine is running. If when a certain coil is disconnect there is no difference in engine missing, you have found a bad coil.