Okay I understand. Could u take a photo form the trunk under subwoofer and stop lights. I need to find a cables from stop lghts to install center stop light. I would be grateful.
I sold my 1990 LS400 in 2003 so I cannot take a photo. The rear lights of 1994-1994 LS400's sold in Europe were wired differently than those on LS400's sold in the U.S. In Europe there were two different versions -- the "German" version and a version for the rest of Europe. You should be able to tap into a wire leading to the stop light in either the left or right rear fender to power the center stop light you add. I think all you will need is an electrical test lamp to find the brake light wire.
This is usually easy. I have added center or twin rear window stop lights to three cars: twin Hella rear window stoplights to a 1983 Honda Accord, a Porsche 944 center stop light in a 1984 Honda CRX Si and a 1986 Mercedes 300E center stop light in a 1979 Mercedes 240D. It was never very difficult to do.