[rpmerf]

I am going to lean toward a bad water pump, partially clogged radiator, or bad fan clutch.

I think it is concerning that your t stat is 170 yet you are running at 190+. It means your system isn't keeping up enough for the thermostat to close.

Where is the sender for your gauge? The stock sender in the side of the head can be effected by heat from headers. Mine read lower with the factory manifolds and heat shields. Intake should be more accurate.

Are you sure you system is well bled? Have an overflow? Consistent level?