[mr0077]

Karl, I'm about to tell on myself, but check this: pull the housing and confirm that the copper button on the T-stat is facing the engine block. I put one in backwards and at speed the pump blows the T-stat open no matter what the coolant temp, at low speeds it doesn't sense the correct water temp and opens late...talk about feelin like a dumba$$...oh, well, cheap check and fix...just cost a T-stat gasket.
Let us know what it is.