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BMW Adaptive Suspension Can Be Added via Subscription. Suspension As A Service (SAAS)
(www.bmwblog.com)
This is a most excellent place for technology news and articles.
The Buick 3800 had a tube like that on top, it would crack from thermal stresses and piss out hot coolant. There was an aluminum aftermarket replacement like you describe but it was Dorman and a cheap fix. Buick also addressed the problem in later versions. I miss that engine.