How do you know the wires are good? Don't assume that because they're brand new that they're good.
After you do jw51's test, and find a cylinder that doesn't cause a change in the way the engine runs after you pull the plug wire off, replace that wire with a spare or switch the wire with one from another cylinder and see what happens.
I have seen perfect looking plug wires be the source of a misfire due to an internal crack or some other invisible problem
