Is it only when traffic is stop and go or is it mostly idle?

First, make sure your air/fuel mixture is adjusted properly for all conditions. At idle you can use a vacuum gage (to manifold) and adjust till you reach the highest vacuum level. If the gage is not steady you have other problems. To rich or too lean can cause an engine to run hot.

Second, verify your timing is set properly. Retarded timing can cause an engine to run hot.

If all else looks okay, try running your advance to full manifold instead of ported. You'll probably need to adjust the air/fuel mixture again (it will be rich). It should run cooler in theory. Just make sure it doesn't ping and you're happy with the driveability.