With the 440 I too had a cooling problem ( flash back to Carlisle 2005 ) but mine was the opposite. Hot in traffic and cool on freeway.
Are you running a thermostat? Maybe the cooling effectiveness of the radiator is lost by moving coolant too quickly through radiator? Opposite thought of Mike's, not lazy but maybe too much pump at higher RPM.
More info on your current set-up please!
PS - I could never get a definate "blankety blank degrees is too hot". My car seems to run somewhat better at over 180 degrees, so that's the thermostat I run. I know on my Jeeps the normal operating temps are 210. Now again I realize newwer vehicles run hotter for cleaner emissions, but many new blocks are aluminum with 210 not being a problem. With my new cooling set-up 210 has been the hottest ever in stand still traffic.
I hope this helps