Unround empty run A8 3.3 TDI

first Hi @ all.Bin new here and would describe my problem.My 3.3 tdi runs in the stand is not round but not all the time so sometimes he catches himself and the world is ok again but unfortunately he runs more round than normal.was already with various mehanics and no one has found anything or have reported any errors on the laptop.Vll you can help me because I would love to drive my car for a while.thx in front