Hate to butt-insky, as I have 126, but you might try removing the entire package shelf. On mine (85 380SE), it comes right out after the rear seatback has been lifted out. The grilles might be attached from underneath, is what I'm thinking, and this way, you won't risk breaking anything trying to pry them out.

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1986 560SL
2002 Toyota Camry
1993 Lexus