I have replaced the cap and rotor and plugs. Next will be the wires but here is what confuses me. At night you can see two of the plugs?wires sparking very lightly. I took one of the wires off of a plug that is firing correctly and switched plug wires but still have the sparking from the same cyclinder and the wire that was sparking before no longer sparks on anoter plug. I know for a fact that the plug is good. You would think that the wire would spark on every single plug i put it on right? Please help. Thanks