I have used several things to get the white wax residue off on my car's plastic parts, rubbing alcohol, alcohol based window cleaner, and several other things. I think they make actual wax remover stuff though, check with your local auto parts store as they can probably help you more than me. In general I try to use whatever stuff I have in the garage that will disolve hydrophobic compounds (wax) but not be bad for the paint or plastic if I'm a little sloppy.
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2001 SE 4x4 5-speed
Super Black