I can't remember where you are from but if you're near San Diego check out SD Truck Shop at Miramar, James is the owner. These guys specialize in Toyota and Lexus maintenance but specifically all the mods you can think of from suspension to Baja racing mods. They race on weekends with what you ask....you guessed it Toyota's. James is a good guy.
When I am off roading on rough terrain I hear what sounds like a door stop spring twaining. I assumed it was just the KDSS disengaging to give articulation. 2015 TEP with KDSS.