Although I haven't tracked down the rough idle yet, I've recently read a 93 page thread about rough idles and hesitation.
I've replaced all of the main things that cause rough idle and have yet to perform a Leak down or compression test.
After narrowing down the possible causes, I've come to the conclusion that:
It may be another vacuum leak somewhere
It may be my rear O2 sensor
It may be my Crankshaft position sensor
It may be something internal
After replacing and researching parts, I came to the conclusion that everything I was doing was not fixing the issue and it must be something else.
I've heard theories:
Lower Oil weight to 5w-30 and it will smooth out idle
The M44 simply always rough idles
Vacuum leaks are always the cause of rough idle on the M44
The ignition components used on the M44 are a poor design
The fuel pump causes rough idle before it fails
The cam position sensor is the problem most of the time
When I bought my Z3 in the beginning of March 2012, it developed a rough idle. I was determined I could track it down and began throwing parts at it.
List of Parts: