Remove the battery cable and measure draw, trunk lights, power antennas. MY 89 SL did the same thing, it turned out to be chafed wires. The always hot trunk light wire somehow fed into the high mounted brake light and drained the battery. The break was near the hinge on the passenger side. There are three wires in the plastic tubing, always hot, stop light and ground, tough to get to. I saw a faint glow from the high mount in a dark garage.
MY2cents it might not help