Only one thing that I've found that works wonders on any plastic and rubber surfaces (including tires):
If you haven't tried any of Adam's products, you really should. It makes Mothers, Meguiar, Turtle, Armorall etcetera want to cry. Trust me.
adamspolishes dot com in case your local retailer doesn't carry it. Stuff ain't cheap, but there is really no competition.
Black 2010 SS/TC – G85 | ZFR6758 | Term2 tuned | 479whp, 470wtq | Built internals | Cryo'd 4.45 | CM S4 clutch | Hahn CP | ZZP IC | Forge BPV | Hahn 3” DP and Catback | Hahn CAI | Ported head & intake | LE5 TB | Opel injectors + custom 5th injector | ZZP S3 cams | 82# valve springs | 420lph E85 LPFP | Custom FM oil cooler | PRS YYZ v3 & Koni yellows | PRS XXX bar | PRS rotated mounts, rear bushings & TCABS | PRS PCV | PRS Racing oil pan | PRS brake ducts