i run 160's in mine, and i drill a small 1/8" hole into the stat, so it wont develop an "airlock" in it. i also block off the bypass from the inside of the stat housing, filling up the nipple with plastic steel, and smoothing it into the top of the manifold at the nipple. this directs ALL the water moving through the pump, into the radiator. the IR gun shows, it works. sounds like you have a bad stat, or two. you can run without it, if needed. or, make a solid gasket out of cork, and pop a hole in the center, the size of a quarter. it will restrict the water a bit, and warm it up a bit faster. i like the 160, as once the engine warms up, it pretty much just stays open, no cycling open and shut.