Audi B7 2.0 TDi (BPW code) Overboosting

Hello! I posted earlier in the mkv forum about my issue but realized the BEW might be more similar to my engine. I’ve started a thread on Audi-Sport.net and am attaching the link here since I can attach pictures on the site.

https://www.audi-sport.net/xf/threads/2-0-tdi-bpw-overboost-issue.405510/#post-3508805

So my basic issue is I’m overboosting like crazy. Problem was intermittent and I have now replaced the MAF and N75 and the problem just suddenly got worse. Actuator moves easily but when I get the overboost issue I hear a fluttering/rotational sound and the car will shortly thereafter go into limp mode. Wondering if the actuator has gone bad? It moves freely and easily. Maybe too easily? Could the egr be a factor? Going to remove and clean tomorrow.

I’m getting a vac pump today and checking the actuator. When you say preload, so you mean actuator arm length?
Thanks!’

Vacuum tested the actuator, it starts moving at 1-2 Hg and is fully retracted by 13-14 Hg, maybe even at a lower Hg number.
So should I assume the actuator isn’t working properly? How can adjusting the actuator arm length change the vacuum level that engages the actuator?

Ok, Thanks! I will try and readjust the arm tonight. But the overboosting issue suddenly worsened this last week, could the actuator arm adjustment have been loose?

Lengthened the actuator rod such that it begins moving around 5Hg-in and stops around 18Hg-in.
Also seemed as though there was/is a slow vacuum leak coming from the vacuum reservoir/vacuum pump vacuum line that leads to the N75. Not bad, just slow and more apparent at lower vacuum. When I increased the vacuum up to 20Hg-in it was almost not apparent. I rechecked all the lines and connections and re-snugged everything and it seemed to help.
As I started driving the car as it was cold (-3C here at the moment) I suddenly had the same fluttering sound, hesitation and the spiky overboost as before as I slowly accelerated. But then I drove very carefully for a few min before accelerating a little harder and things seemed to improve. The log graph started showing almost perfect alignment between requested and actual boost and low-down power was improved with no hesitation.
I think I still have a slight vacuum leak that is more apparent when the car is cold and the engine hasn't built as much vacuum. This seems to be part of the cause of the weird overboosting and fluttering sound. But after driving 20km at all speeds tonight, it now drives better then ever since I bought it.
So to sum up the story: the actuator arm seems to have been too short combined with a slight vacuum leak to the N75 system caused my weird overboosting issues.

Thanks for the help as always!

Possibly the engine heat helped a vacuum seal get better? Either at the end of hose or a crack in a vacuum hose. Is the hose old?

Hoses are a little over 3yrs old. Will smoke test and replace.