I don't think it's the TBM causing this. I wanted to check to see what these fps problems were that people were questioning. After 6 hours of X-Plane running, with the TBM loaded, powered up on the ground running off the GPU, all avionics running, my fps remained 100 % constant at an average of 30-35 at Saba airport.
Do you have any other plugins? If so, how many? Have you tried removing them and then running the TBM? If you still get a slow down in fps, can you post your log.txt (found in the root X-Plane folder.)?