Hi, having the same issue with my 4runeer 2011 Trail Edition 200000 km. I have the car for about 1 month and just felt it: vibration when slowly accelerating. It's happening mostly when 3gr ~1500 rpm shifts to 4th ~1000 rpm. Vibration disappears at around 1200 rpm. It's like when driving a manual transmission and you are in a higher gear and there is not enough power.
I'll try to lube the driveshaft U-joints first.
I'm not sure how are you guys adding the shudderfixx....
Then eventually will replace the front driveshaft U-joints I guess.