Fried,

If you have a voltmeter make sure that DA#1 has zero voltage when the key if OFF.

How do you know there is a drain on the battery? Is it discharging or have you found a draw with your meter? Killing individual circuits by pulling fuses can isolate a circuit and narrow your search.

I believe some modern electronic gadgets like digital clocks or CD players may draw a tiny amount when energized...could this be what you're seeing.

A bum alternator can discharge the battery too.

Stuart