Since you've replaced your nylon bushings with metal ones, you may have tightened up your linkage to the point to where it transmits in vibrations from the engine compartment.
He meant silicone rubber. He's using it as a soft rubber gasket to be a vibration dampener. It's at the auto store next to the glues. Since you've sprayed WD40/silicone spray, you'll need to clean it off for the rubber to stick. B-12 is great for this but can hurt everything else. BE VERY CAREFULL WHAT YOU PUT THIS ON! Maybe spray it on some cloth and just wipe with it. Put WD40 on a cloth and lightly wipe any surface you want to rotate/move after it cures.
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