I bought some Duster taillight lenses at the Nats that were all goobed up with some sort of black tar-like substance around the edges. Apparently someone in the past had tried to seal a trunk leak. I was able to get most of it off just by pulling it off but there is some left that is smeared on the lenses. I would like to know if anyone can recommend what I could use to clean it off that won't tarnish or otherwise harm the plastic lenses. Thanks.