Catalytic converters will cause a sulfur odor.
However, before jumping into those, switch gas stations for a few tankfulls. Make sure the stations do not get their deliveries from the same tanker truck. Occasionally, a refiner does not remove enough sulphur when refining to gasoline and this can contribute to the odor you have described.
There was a service bulletin a few years back in which Ford released upgraded cats to help with this problem.
Steve
