Hello man,
I never found the issue unfortunatly. Along the way the car got dpf and egr problems. Which led me to do a egr delete by software and the 2 dpfs got welded out on the inside to make it like a straight pipe but still looking original. This helped alot and was almost not noticable but since I knew about it i could always feel it. And mpg was also going up. What I heard is that the Electronic actuator needs to be calibrated on the car. I personally couldnt find anyone that could do this for me not even audi themselves.
Just 1 week ago I changed it at a car firm and bought myself a mercedes a250 4matic. I really liked my audi bitdi but all the problems that i had really gave me depression. I hope you find the issue and if you do I would love to know what it was.
Also I changed 2 throttlebodies and did stage 2 along the dpf delete. Good luck man. I would try to get the injectors cleaned at least the loud one.