Hi all this is my first post not sure if this is the right place but here goes.

I have a 2014 a6 3.0T (C7) with ~71000kms on it. The issue is that while going above 70km/s if I accelerate, I feel a judder/vibration in the acceleration pedal. I can feel it from 70-95kms after that its not really noticeable since highways are not the smoothest where I am from so not sure if its the road or not.

-I did an oil change (5w-40 from the dealer)
-Changed the air filter
-spark plugs are good
-new front bushing/wheel bearings
-got the tires balanced and no bends. (snow tires right now with oem 19 wheels)
-It only happens in D mode, might be happening in S mode but its not noticeable, probably due to higher rpms?

I am thinking maybe its the carbon built up? suspension? or transmission issue? or something else? not sure the mechanics cant seen to figure it out
I have booked an appointment with a new mechanic next week , just wanted to know for any potential issues.

Any help would be appreciated thanks