Thick rag with solvent (acetone). Screw/twist the surface till the brown stops showing.
I never killed a set of plugs. Have heard reccomendation, change every 3 years or 300 hours, which ever comes first.
Been following force/chrysler forum for years. Surface gap plugs trolled for extended times will foul.
Plugged recirculation system will cause performance issues and excessive smoking.
