When they are that far off at an idle it's usually an intake manifold issue. Most times it gets amplified with RPM but I have seen some stuff that had wacky distribution at idle that cleaned up as RPM went up.
If you are going to really sort it out it should go on the dyno.
Also, I could be nuttier than a jar of goobers and it could just be a tuning issue.
I've been wrong before.