Who has fought & solved unstable idle issues? (M54 3.0)

[Bdc101]

I have been suffering some symptoms over the last year or so in my 2003 X5 with M54B30 (5-speed manual):

1. Fuel trims exceeded codes in DME but not on dash (frequent)
2. Fuel trim codes on dash occasionally (only on long drives and only a couple of times)
2.a. I haven't kept perfect records but I believe I am getting only lean codes, not rich.
2.b. I do get these codes on both banks 1 and 2 at the same time.

3. Unstable idle: on/after long drives (only when completely warm) car will stumble when putting it in neutral and sometimes die.

Using both this forum and Bimmerfest I've learned that these sorts of problems can be caused by a variety of things including MAF, vacuum leaks, ICV, DISA, and others. With this in mind I have checked/fixed the following:
1. Replaced intake elbow (3 yrs ago, but have double-checked the integrity recently).
2. Removed and cleaned idle control valve with brakleen. Verified that it is freely oscillating when the key is in the "on" position. The valve was dirty but had no real buildup that was visible.
3. Inspected airflow meter and verified integrity of all downstream clamps, vacuum lines, and hoses. (Note that I have not replaced the MAF and may do so if I have no better ideas.)
4. Replaced DISA with the GAS upgraded unit and O-rings.

I see a plethora of threads describing the problem when searching, but few actual solutions. For this reason I am starting a new thread and would be grateful for anyone else to share their experience with problems of this sort and how they fixed them. Thanks in advance guys!