Echo: what is the opening temperature on your thermostat? I went down from factory to a 180-degree to give me a little more margin in the summer.
Do you still have air trapped in your cooling system (don't forget your heater core)?
Not to insult, but if you have a serpentine belt system, I assume you put the right rotation fan and water pump on there.
Consider changing the thermostat to a high flow model - drill three 1/16" holes around the rim, inside of the gasket to help let bubbles out prior to the t-stat opening.
Finally, If there are no obvious answers, consider adding water wetter (I use Red Line, but there are other brands) to your coolant to help it pull more head out of your engine.