That kind of thing depends on the FOV you use. It's probably the side of the seat, and the part of the seat even nearer to you got Z-clipped.

But i think have a little bug.The rear window's warm system lines not very visible :S I think make a bit sharpness that.And take rev-limiter to patch Z pls ^^ (Its not a big update but that take lfs to more realistic)
now I can't unlock it as I had none left