Where do I begin.
ECU failures.
Solenoid failures ( A pair of these above each cylinder and they live inside the valve covers).
Exteme wear in deactivated cylinders (due to the always malfunctioning TB injection pooling fuel at the closed intake valve of a deactivated cylinder).
We used to convert these cars to run without the deactivation as the solenoids would sometimes stick halfway open and closed in cold weather.
Now I am sure that modern technology has taken care of all these problems but for the 1 or 2 years they made this motor I am sure the failure rate of these early examples was at least 90% where I worked.
I would like to see a nice running example again though!