Q: Duel exhaust on 98 f150 shakes when idling . Every so often get a fuel smell in cab

The engine is not running well and combustion is not complete hence the fuel odor. However, fuel odors can also be caused by leaks and so that possibility should be considered, too. Rough operation could be due to a bad tank of gasoline, dirty fuel injectors (at the mileage you report, the injectors should be removed from the fuel rail for professional off car cleaning, and internal filter replacement, and that step alone may resolve your issue), incorrect idle speed, exhaust restrictions, vacuum leaks, incorrectly installed or damaged spark plugs, a defective or clogged fuel pump or fuel filter, failing electrical components such as the ignition control module, plug wires, coils, and spark plugs, a defective airflow sensor, dirty oxygen sensors and other causes. I would recommend that you request a rough operation/rough idle diagnostic and the responding certified mechanic will perform the required diagnostic steps to get this resolved. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.