You have an intermittent parasitic draw....lucky you. Unfortunately that can be one of the biggest pains in the asses to find because its intermittent, and because you have to wait an hour for all the modules to go to sleep in many cases. Usually that kind of issue requires a specific test with some BMW factory tools (GT1 or DIS). I'd suspect the wiring in the trunk, and did you bypass the neg battery terminal on any of your rewiring? The terminal should contain the IBS monitor and bypassing it can cause all kinds of annoying stuff.