FCP Euro:

https://www.fcpeuro.com/products/bmw-engine-intake-manifold-adjusting-unit-11611440049

 

This price seems about $100 too LOW.

I'll ask - what is the difference between a MADE TODAY 'Genuine BMW' and say a Siemens/VDO?

 

FCPEuro!

 

If yours is original BMW I'd consider rebuilding it with one of these kits from GAS. These only fit genuine BMW DISAs and not aftermarket.

https://germanautosolutions.com/store/bmw-m54-25l-disa-repair-and-upgrade-kit/

The redesigned aluminum flap and bell crank are a much better than the stock plastic parts and won't fail again like the original ones do. You'll save about 100 bucks and end up with a part better than stock.

The only other failure point seems to be the vacuum diaphragm which can also be replaced. More info on that here:
https://forum.e46fanatics.com/showthread.php?t=1205601

 

Great kits (I have one in my car) but... They won't fit his M52.

 

FCPEuro. Period. Lifetime warranty.

 

https://www.daparto.de/Teilenummernsuche/Teile/Alle-Hersteller/11617544805?ref=fulltext try a search here. No clue if they ship to the US of A