what the way they were shaking? my back seats in my car do that as well... my trunk is like the inside of that truck when it comes to flex.

 

But the real question here is, do you have leather seats? (YOU DO!)
I just haven't seen a lot of videos of people with a flex with leather seats inside their vehicle ...

I mean, I DON'T have leather seats (nor do I think I'd ever get leather seats, ever again - sticky in the summer, cold in the winter) ... that's all I'm saying