Are you using the Motronic Diagnosis data at
this link? There are several
No Spark checks and a couple of
Hall Sensor checks. They involve BMW's proprietary tester but most tests can be reproduced with a good quality multimeter. It's probably best to ignore involvement with ABS wiring right now. One point about the ingnition amp is that its contact surfaces must be cleaned and then covered with a thin layer of heat shrink paste so they make full contact with each other. Attached is one of the
No Spark resistance tests from the manual.
Does your Brick still have functioning diagnostic plug that you have tried to use?
Maybe Scott_ will chime in here with some observations.