Are you elevating the front of the truck (like on ramps) to make the radiator the highest point in the cooling system when the truck is running? It's what I alsways do when I wanna get all the air out. I've had the loping problem before, and it was always because of low coolant or air.

93 4runner V6, 4.88's, 31" mt's with more to come.
03 Tundra V8 on 265's