I've had fabulous results using Griots Garage Vinyl & Trim Detailer over the last several years. Here's a link:
http://www.griotsgarage.com/catalog.jsp?L1=L1_1000&L2=L2_1002&SKU=11169
I use it on all black / gray bumpers, plastic trim, rubber, moulding, tires, etc. and it doesn't leave any sticky or messy residue...just a nice perfect satin sheen.