[mpathic]

Consider the DISA a 100k miles service item. Avoid the Chinese knockoff cheap DISA ECS sells. Bought one and it was cheaply made low quality. Stick with BMW brand or OE. There's also the Australian guy on EBay who sells a nice DISA upgrade kit with metal replacements for the brittle plastic parts.
You can also place a bead of silicon rubber on the DISA's seal to the intake manifold to prevent slight vacuum leaks that will drive you nuts looking for after seemingly random "Fuel Shutoff A" and/or "Speed Sensor A" CE.
It only will blow a motor if you ignore the sometimes rough running and CE codes that are telling you something needs to be checked out. The pin and flapper will only go gonzo and down an intake port after more than sufficient warning.
When a DISA is getting cranky, you will most likely see one engine bank running abnormally leaner than the other intermittently depending on engine temperature.