There's a product called "showroom new" that I use on black plastic parts and rubber.
http://www.ebay.com/itm/Auto-Plastic..._Tools&vxp=mtr
It's a black dye, so there is no peeling or flaking. It soaks into the plastic for a deep black look. A little goes a long way. Be sure to use rubber gloves when applying it, or you will have dark fingers for several days.
Another consideration. Black Rit dye. You can pick it up at Walmart or any craft type store. It's for clothes, but I've used it on faded black plastic.
One other product you might be interested in. Black Wow Exterior Trim Restorer.
http://www.ebay.com/itm/Black-Wow-Ex..._Tools&vxp=mtr
I love this product. It's some type of oil and a little goes a long way. It brings out the original color in a lot of plastic/rubber trim pieces. I can't say I use it regularly, as all the plastic pieces I've used it on, I've not had to recoat since.