I found a sample tube of Solution Finish Black Trim Restorer in an old waxybox and decided to have a go at the expanse of "black" plastic that sits under the windscreen on the BRZ. There's also a plastic diffuser which could do with freshening up, but I'm only trying this area initially. As you can see below, it's gone that nasty grey (it's a 2013, so it's not like it's seen that much sun).     Sadly I dropped and spilt the sample tube after only a few inches of work, but it was going fine