Looks like you could do with logging software or someone close to you with it who can help out, you need to do a few logs driving in the fashion that provokes the power oscillation.
Hopefully the data can prove whats going on.
A few logs with revs,IQ,desired boost,actual boost, vnt%, maf airflow,desired maf,atmospheric pressure.
Should help go a long way to see whats going on.
Regarding turbo vnt actuator, get someone else to start the car while you watch the actuator pull the lever to the stop smoothly, get them to stop the car and see the lever return to rest(open) position again smothly , should take a couple of seconds max opening and closing.
A 5 min test max. Tell us what yours does.
vnt operation for youtube.avi - YouTube
This is what you want to watch(mines on a bench though) so it should just pull towards you on start up , stay there at idle resting on stop screw, on switching off it should move out around 8-12mm not sure on the 2.4?
Also a quick check atmospheric pressure to boost pressure with just ign on to see how realistic map sensor is , i had a cheap map sensor not bosch that ran fine for a few months then on accelleration on carriageways etc i would see the same boost up n down without moving acc pedal off floor. bought new bosch sensor been ok ever since.