Mine will go to 200* after a cool morning start. I've seen 200* on cool mornings after a run to work (stop-n-go) and letting it idle for a bit. Most of the time I cut it off at 300*. Normal afternoon temps will drop to 300*. On hot days, it takes a little bit of idling to get back to 300*. Highway cruising @ 70mph, I see 600-700* - When I'm pulling my 5th wheel up a grade I've seen it go as high as 1300* so I back off the throttle a bit to keep it @ or under 1200*.
I'd reccomend checking all your connections.