Are there any products out there that WORK for de-yellowing head lamp lenses?
Yes.
Visit your local Pep Boys/Auto Zone/Advance Auto/O’Reilly, etc and you should find some of these products.
I understand that the kit from Mother’s, which includes a buffing head to attach to a cordless drill, is very good.
Mequire’s PlastX works well with a cloth, too, though VDC’s Mother’s solution sounds even better
I’ve had excellent results with polishing compound and a sponge-type drill-mounted buffing pad, keeping the pad (and thus the compound) plenty wetted.
I use 1000 grit wet/dry sandpaper followed up with 2000 grit wet/dry (both used WITH water) and finished off with MeGuiar’s PlastX.
I just replaced the lens. For $70 a pair, it seemed like the better deal. I’m sure replacement VW lens will be quite a bit more pricey though.