I have never waxed my truck, but the dealer must have! There is white residue of car wax on one of the plastic side vents in front of the front doors. I assume there is a product to remove this?
Use some Tire & Rubber Cleaner with a microfiber towel. If the residue is deep in the texture of the plastic a small detail brush or soft toothbrush can be used to scrub it out with the Tire & Rubber Cleaner.
I have had some success removing the residue with a pink rubber pencil eraser. This has been my go to for years on textured black/dark plastic surfaces. I keep one of the large erasers with my wax kit. Check YouTube. You should be able to find some videos there too. Good luck!!