High rate of battery discharge message

[andrejgo]

HI.

Recently I bought a bmw 650i e63 2007, I live in Europe and car was imported from USA. After a week car started to show me high rate of battery discharge message.
It usually comes up few hours after it has been parked.
First week car was parked in a garage and it had no problems, then I installed an anti theft fuel cut off switch by an electrical shop and the next day messsage started to appear.
I asked them if this switch could be the cause, but they are sure it is not, as they installed many of this switches on bmws and never had a problem with one. (I heard that cutting/extending wires could give wrong signals to computer)
So i was told to change car battery, that did not help, I also changed IBS sensor, also computer was told it has a new battery, but the message is still there!
I don't know what to do next. I am thinking of taking fuses out overnight one by one, any other ideas?

[andrejgo]

Another thing I just remembered, at electric shop they also replaced one rear license plate bulb which was broken (there was also replace bulb sign everytime I started the car),
could this have anything to do with it?

[witeshark]

Could be; there me be a short or bad ground around that light.