I saw on Youtube how you can rejuvenate plastic with a heat gun. I had 2 Burnt Orange kick panels and decided to try it. This was the worst one, it was extremely chalky. and almost unusable.
I heated it and it took a while for to to "gloss" up. I went over it very carefully at first. It started looking pretty good (almost new) on the non chalky part.... I was very surprised however, to see that the chalky areas (although darker than the original) were turning back into plastic. As I went on I got more aggressive. If you go slow and heat each area slowly you can keep warpage to a minimum. I used cold water after and cleaned them up. Pretty satisfied. I still plan on painting them.

Impressive, I have a set I need to do this to

that is impressive, thanks for sharing & yes youtube is a goldmine

They are made of Polyethylene, consider it to be very similar to a hard wax in the way it moves with heat. You are simply melting away the degraded areas and leaving a shiny (melted) surface below. You can't make it "turn back into plastic" with heat, but a minimum amount of melting can improve the appearance as you've discovered.

Used to fix scuffs this way at the dealership. To much heat will make a mess. But the right amount works pretty well. After a while you'll be able to judge how much by watching the part.
Doug