Throttle body spacers are not going to give you any measurable gains in fuel milage, despite what the manufacturer states. They make good paper weights or door stops though. If they were as good as they are stated to be by the manufacturers, the auto industry would have them on from the factory to help their federal required fleet fuel mileage requirements.
Save your money.
"Never argue with an idiot; they'll only drag you down to their level, then beat you with experience"
2007 F150 STX Supercab (4.6 2V V8), Edge tuner, factory navigation, H-D headlights, Mark VIII electric fan conversion with flex-o-lite controller.