The problem ain't all that hard... apply a little logic...
First check out the RedTop... it can still go South on you. Be sure it's good and can hold a charge for a while...
1. Find ALL the circuits, and their fuses.
2. Remove half the fuses and let 'er sit.
3. If the problem still exists, the problem is in the fused circuits.
4. If the problem does not exist, the problem is in the circuits where you pulled the fuses.
5. If the #4 is true, then put in half the reamining fuses and see if the drain occurs.
6. If the drain occurs, the problem is in the circuits where you replaced the fuses in step 5.
7. If the drain does not occur, then put half the remaing pulled fuses back in and let 'er sit again.
8. This is gettin' repetitious... but I think you can see the point.
You're quiclky narrowing down the circuit that has the drain and then once that's done you identify all the devices on the circuit and remove them. If the drain occurs... the problem's in the harness. If the drain does not occur, then replace half the devices back on the circuit... it the same thing you did with the fuses.... only different...