I installed a Whiteline insert today, along with a Barton two post shifter bracket. The Whiteline insert definitely adds vibration, but its not all that noticeable during normal cruising. I modified the insert by cutting the center rib off completely. I'm glad I did, because as it sits right now its just on the verge of being noticeable while cruising. When you get on it and the RPM'S climb, you can definitely tell something is different. You can feel the vibrations through the shifter and the floor boards (I felt it through the clutch pedel lol), and most significantly the audible noise in the cabin is greatly increased in the form of an engine resonance...though nothing rattles or vibrates.
That said, as soon as you back off things return to normal. I have a feeling if I hadn't modified the insert I would be annoyed with the increase in NVH. But the difference it makes is astounding. High RPM slop is greatly reduced. The combination of the shifter bracket and the mount have made the gear changes much more positive and reliable. Before whenever I would shift at high rpms, above 6000, I would have to purposely pause before going into second due to the slop of the transmission. Now it is a much more positive engagement...you can tell the car is still trying to fight you but it simply can't resist and the gear plops right into place. This is about as good shifting as the MT82 is going to get, which with the modifications is actually VERY good for a car off the lot.
The Aisin 6 speed transmission in my FR-S was better, but not by much and only after I changed the fluid, and that transmission is loved by virtually all so I feel its a good benchmark.
At the same time I did the insert and the bracket I also changed the fluid to Amsoil MTF. MTF is a thin syncromesh formulation at around 9-10cSt. Not as thin as the ford dual clutch fluid at 6cSt, but not nearly as thick as 14cSt gear oil that the original cars came with in 2011. My car was a 2012 model year which could of had the original gear oil or the double clutch fluid as I haven't checked the manufacture date. Either way the fluid in there was terrible. I would always get a nibble when going into second gear, especially when cold. Granted I've only done a short amount of driving since the swap this morning, and its 95 degrees today, but things seem improved. I have not gotten a nibble in second and the transition into the other gears seems....slicker. The only way I can describe it is the shifts seem better lubricated, slicker and with more "cushion". I used the same fluid in my 6spd Aisin unit in my FR-S. That transmission calls for a 75w-90 gear oil and many people reported much better results with syncromesh formulations. MTF in that transmission CHANGED EVERYTHING. It was amazing after the swap and it continues to impress me in my MT82. Also, being marginally thicker, it theoretically will offer more high temperature protection, which I can appreciate as I roll into summer in central Texas