It's probably your lights. My truck started having highway speed over heating after I put my winch on. ONLY above 65 mph. Must be disrupting airflow at that point.
If it doesn't over heat at low speeds, I think your losing airflow across your rad at high speed.
Only other thing I can think of is your lower radiator hose sucking shut at high rpm's. Never seen this on a Toyota but, I have seen it on other equipment. Usually on hoses that are supposed to have a spring inside to keep them from collapsing but, are missing the spring. Also seen it on oil soaked hoses that get real soft. You said new hoses though.
Did the problem start after you put the bumper and lights on?
