I've been fighting a similar battle with my 03 Eclipse for 2 years now. I've finally gotten it to where although it runs hot in stop-n-go traffic, it doesn't overheat.

What I've done so far:

1. Shop replaced temp sensor. They replaced the wrong one though. They replaced the one for the temp guage instead of the one that turns the fan on/off.

2. I replaced the correct temp sensor but it didn't help.

3. I replaced the water pump (was told that it could be that the vanes on the water pump were eroded to the point that it wasn't moving enough coolant). That didn't fix the problem either & the old pump looked fine. BTW, I replaced the timing belt while I was in there.

4. I replaced the thermostat twice (once with aftermarket & once with OEM). That didn't fix the problem either. I'm running without a thermostat right now.

5. I tried repeatedly to burp the system with no success. I was told that the system could get a bubble behind the thermostat which would cause it to not open. I even drilled a hole through one of the thermostats to allow any bubbles to seap through.

6. Replaced the relay that turns the fan on/off. It was dead & now I can drive it without the fear of overheating (even though it still runs hot according to the temp guage).

Eventually I'll put the thermostat back in & probably replace both temp sensors again but there's no rush. The only problem I have running it without the thermostat is that I get a CEL about once a week during the winter indicating that the engine is running too cool.

I know the vehicles are very different but maybe you can glean something from my trials.