It looks like plastic surrounding the top of the bed of my 99 F-150 and on the front and rear quarter panels.Maybe it's vinyl. I use Meguiars vinyl and rubber cleaner # 40, but it doesn't work too well. Any suggestions?

 

I forgot to mention, i want something that will revitalize or darken the trim too in addition to cleaning it, unless there's something that does both. I am reluctant to try the magic eraser for cleaning based on some of the negative posts.

 

I know a little bit about plastics, and I don't think the bed-rail caps are vinyl based. More likely ABS, or an ABS blend of some type. I doubt you can "clean" them back to black, as the graying is most likely UV damage. I think this has been discussed here a little bit in the past, might find more if you dig through the archives.

 

To remove any wax from the rails you can buy a can of "Tuff Stuff" interior cleaner (its in a yellow can with red top) from your local auto parts place. Auto Zone and Wally World both carry it here. Use this and a soft brush to remove the wax and wipe it dry with a towel.
While your at the parts place pick up a bottle (its red) of "Back to Black" and follow the directions on the bottle.
Been there done that with my '01 SCrew when I had it and it worked wonders...Might take a couple of applications but it will work......

 

I agree, Mother's Back to Black is great.

 

MOTHERS bumper black