A short answer on those gizmos - don't bother, they don't work.

Some engines just aren't as efficient as others - plus environmental factors and general engine wear and tear all contribute to gas consumption. I usually get around 12-13 MPG on my VX in the city - it goes up to about 16-17 on interstate driving trips. The more performance mods you have, the worse this gets - mostly because the mods introduce higher airflow or more fuel boost - this creates better response times and usually causes the driver to drive more aggressively - it all contributes to poor gas mileage. Remember the VX weighs in excessive of 2 tons with a driver - the full ladder frame and full-time 4wheel drivetrain all has its toll on engine efficiency. If you're looking for a gas saver, buy a motorcycle and swap off driving every other day - the VX just isn't a good candidate for economy gas mileage.

-- John