Charger 68 440

ok so me and my dad have a 68 charger with a 440 magnum engine we had it running perfectly then we decided to make it idle lower when we did that it started skippen on three cylinders two on left and one on right we changed spark plugs the coil, distributer, points, cap, went threw caburater and checked compression and now we dont know what else it could be plz let me know what you think thanks.

octane

If you have to larg of a cam it can do that at a low idle.