misfire on 90 deville again

I have a slight misfire that I can't figure out. I can unplug each injector and the idle changes but when I disconnect each plug wire and the idle doesn't change so I'm thinking that its something with the ignition but what, cap and rotor are brand new so is the wires.

So there is no change on any of the 8 plugs as they are disconnected, that is really not possible, it maybe hard to detect the misfire from the miss caused by adjoining cylinders being disconnected, pull the plugs and look at them, you may be able to see the problem.

I have a slight misfire that I can't figure out. I can unplug each injector and the idle changes but when I disconnect each plug wire and the idle doesn't change so I'm thinking that its something with the ignition but what, cap and rotor are brand new so is the wires.

How old are the plugs?

The plugs are about 4 months old, I'm going to pull them and see whats really going on