I had REALLY grey bumpers when I got my 8 valve and I tried a couple of things like ArmorAll, but it didn't really do much (armorAll actually turned the small area i tested slightly brown!). The best solution I found is CarPlan Black Trim Wax, which you can buy from Wilkonsons. It is a black, wax-like liquid and I was amazed with the results. I wasn't expecting much, but it really did a good job restoring my bumpers. The first time I applied it, I did a coat on a saturday and really spent some time working it into the plastic. The next day I went over and gave it another good coat and it looked brilliant. What is best is that it lasts. I tend to just give it a really quick rub over once every couple of months just to freshen it up, but the final look isn't gloss and it looks natural, so I recommend you give it a try.