So, I use a Thrustmaster T16000M setup and run the game almost exclusively in VR. To add, I have not had this issue with any vanilla or DLC aircraft.
However, when I download an aircraft or two and insert them into the files (Yes I did it correctly, I have double and triple checked), they all seem to have the same bug. I throttle up for takeoff, as you do, and as soon as I am airborne the throttle has a mind of its own in-game. My physical throttle is at 100% but in-game it goes down and up on its own. I pull a high-g turn and it throttles up. I level off and it throttles down to the point of an eventual crash into the ground. I have scoured google and I cannot find mention of this problem anywhere. Below are the two aircraft that I have tried it with thus far.
If you have any knowledge of this issue, please help. The community creates some amazing things and I would love to partake.