Genuine gear is really strange. I like to think of japanese workmanship being pretty good, but even with big name companies it can be hit and miss.
I know a mate who got (from memory) Dmax carbon roof wing, rear lip etc for his S15. The roof wing is the worst for finish, fitment I have ever seen. Overall it is disgustingly bad and was purchased through a reputable shop as a genuine dealer I believe. That said, the lip was good.
That alone sometimes scares me from spending oodles on legit stuff I've never seen in the flesh.