One issue that I have with laying this issue on the fuel system is that the car seems to do fine on a long drive and only acts up when you hit heavy traffic and the underhood temps go up. Someone mentioned that knowing what year and model the car is would be helpful. I'll second that.

If this car has a Bosch control system( small ignition control module separate from the coil), I would be very suspicious of this ign module overheating and causing your trouble. Since automotive diagnostics is my profession, I like to verify the cause of a fault before I replace parts. Of course installing a new fuel filter is always a good idea if you even think it might be an issue. However, if the problem continues, I would suggest a spark test the next time the problem occurs. You can do the test using a spark plug laid against a metal part of the engine, or using an inexpensive spark tester that will flash when there is spark. The spark tester makes the test easier when you're alone as the flash is easier to see. If you find that there is no spark when the problem is present, suspect the ignition module.

To test the module,use a 12v test light to check for the primary ignition pulse(PIP) at the coil's B- terminal. The light should be steady with the key on, then flash when you crank the engine. This test is easier with a helper. Since failure of this module is common, it is a good idea to carry an extra with you. Then, if the problem arises, you can just swap in the spare and you'll know right away when the problem is solved.
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