Auto and manual computers are different and you could burn a circuit in the ecu if swapped. The o2 sensor circuit is wired different.
147ma is a small amount of draw. That shouldn't kill the battery over night. There are a bunch of circuits that run through the computer that could be causing a draw.
Have you checked the condition of the electrical part of the ignition switch ?
Remove the computer and open the case. Check for gunk around the bottom of the capacitors and for burned traces on the board. Also, like above, smell it to see if it smells like burned plastic. Check for melted stuff on the board. If it's causing the draw something shorted out and will be melted, burned, cracked, or throwing up on the board.
If the battery reads above 14v running at 1500rpm and goes to 10.**v when cut off for a few minutes the battery is probably bad. When was it last replaced ? I've seen 3 month old " new " parts store batteries go bad.