Help needed - where is the engine control computer located?

[xchen]

2008 X5 3.0si, with about 115k miles. It had check engine light on and my DBII code reader fetched P0306 for cylinder #6 ignition misfire.

I replaced the ignition coil, spark plug and the injector. After a short drive in the neighborhood and it still has the P0306 code and check engine light on. The engine runs slightly better than before but still rough at different times, idle or acceleration or both (does not seem to follow a pattern). Some one has suggested that it could be a bad engine computer (ECM?) and I have no ideal where it is located.

So, anyone knows where it is placed and what it looks like?