Try this stuff, it has worked miracles for me. The cleaner (#17) goes on first, then you do the polish (#10). I never tried it on guage plastic, but I don't see why it wouldn't work on that as well.
Edit: I would actually skip the cleaner (#17) on guage plastics just because it's a little abrasive. I'd go straight to the polish (#10) and see how that works.
__________________
2007 4Runner SR5 4.7L 4WD, Toytec Ultimate kit, 285/75-16 BFG KM2's, TRD rims, UrbanRunner rack, SE hood, couple other little things here and there
