Being connected with speed makes me think it's wind noise maybe? Some of the higher trims have a rubber flap on the front edge of the rear-door for this reason, which sounds like the same area you're hearing from.
As a proud new owner of the only certified pre-owned SR 4x4 MT in the country, I'm curious what people think of the leaf spring rear on the SR? How does it compare to the coils? Are there hammer-hangers in development, or is that not relevant anymore? Is there any aftermarket support for this...
These Tuxmats look amazing, and I love the coverage. Do you have any concerns about the durability of the material they use? Almost looks like vinyl upholstery, which worries me a little.