Update. I installed 5100's all around and set the front to the 2nd setting which is approx .85" lift. My alignment guy was able to get 4.0 and 3.8 degrees positive caster. HUGE difference. I love the 4R now! It drives how it should have come from the factory. I can't stress enough how much of a difference tires and the 5100's with the front lift and firmer spring rate and the CASTER adjustment made..... Tires helped a lot with the marshmellow feeling on my SR5, but the biggest difference and bang for the buck is the caster adjustment.
So to recap, yes the tires helped, so did the shocks, but it was the CASTER adjustment that made the largest impact on how the SR5 handles and drives down the road. I'm loving my 4R now, and a couple of weeks ago I was thinking of when I could sell it...
I've owned three 4runners and 3 tundras, I know how these things should drive and the stock sr5 wasn't right.