Hi, the black streaks that you mention, do you mean the dirt spots on the top of your bumper on the picture? If yes, that's normal. The rear of a CT gets dirty very fast when driving in the rain. It's just caused by the design of this car. Some people fitted mudflaps and it supposed to get less dirty but I can't tell for sure since I haven't fitted those.
The part that's missing is this I think:
Cushion - Lexus (75129-AC010)
2002-2018 Lexus Cushion 75129-AC010 | Longo Lexus2002-2018 Lexus Cushion 75129-AC010parts.longolexus.com
Thank you! Cause on all my previous cars I never had any spots whenever driving in the rain including my 2001 Lexus is300. Wasn't sure if it because it was DESIGN of the car or its WHITE Color.Interesting. My 2016 with 30k miles has the same exact hole situation, even with the same dirt lol. I wonder if that's some sort of drain hole.
View attachment 62433
And the black spots of dirt on the back are because you drove in the rain. Just doing it once will make it look like that (doesn't matter if you washed it). Mudflaps won't help, because it's the way the air comes over the back of the car.
Any way to prevent it or increase time between washes? Thank you!