Two I have recently dealt with, the first had suffered with water ingress to the valvetronic ECU but this one did put up the odd code and the water ingress was obvious when I opened the ECU.

The other was similar to yours, no codes, with very rough running which smoothed out when the actuator motor was unplugged (forced to run as though non valvetronic engine), this one occasionally turned over as though there was no compression and when trying for wide open throttle would bog down, motor checked out good and appeared to learn stops OK.
This one was the eccentric shaft sensor at fault.

Hope this is of some help

Cheers

Steve