Give me good brain, watch the wood-grain
Don't want no cum stain..bitch, you listening?

from Eminem (Ft. Pink) – Won't Back Down Lyrics on Rap Genius

Meaning

“Brain” is a slang word (derived from “head”) for oral sex

Wood grain paneling is considering luxurious on the inside of a vehicle (on the outside it’s just tacky)

IF YOU PUT IT ALL TOGETHER: Eminem’s telling Mariah Carey to suck his dick and swallow (to avoid staining the interior of his car)

Reasonable request, I think..

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