A few things to mention before we proceed further.
It's impossible to make a comparison between the default Cessna and the TBM. The Cessna has minimal textures, minimal mesh and probably a few hundred lines of LUA code.
The TBM has hi res 4K textures, multiple objects, and about 200 000 lines of C code. So in saying that, the code is always doing something, and it might have a small drop in fps for a second, but it's rare.
You failed to mention what fps you are getting. What does it drop down to?
Other factors can contribute to a drop in fps. Scenery loading is one.
Could you also post a log.txt file so I can see what'd going on while you're running the TBM?