Does anyone know of any common Key off-Engine off power drains on '05-09 Mustangs?

I know it's an old thread, but my '07 GT500 came with the crappy Shaker 500 and I always have had battery drain problems. I spent hours doing proper load tests and never could ID any circuit that was causing it. Installed an aftermarket (Pioneer) head unit and it still does it. I hate having to keep the car on a trickle charger - it's the one thing I hate about this car.

 

Mine is the same but I have replaced the map bulbs w/LED's so that's likely the source in my case. Stock stereo and like you I have to disconnect the neg cable of the battery to prevent batt drain. The problem has killed two batteries over the last few years. Got a digital charger to keep the battery conditioned. So far, so good.