Does it have normal power? It does. Runs great!
Have you run it with no thermostat? Haven't tried that but we've replaced the thermostat 3 times now in the last year.
Has the water pump ever been replaced? Yep, no change
Has anyone checked the actual coolant flow? I don't believe we have done this but I'll mention it to the shop. The did 'vacuum fill' the block and radiator with coolant in case there was some air bubble or something ...no change.
I'm thinking checking the coolant flow might be the next thing to check. Other than that ??????