E-bay Rip-off Items
The IAT Resistor Mod
These are marketed as "speed chips", come in many creative packages, and claim to "boost" your horse power by 20 or more. Surprise, it's utter bull shit, and eating lucky charms won't make you fart rainbows either.
The electric Super or Turbo charger
These are usually bilge pump blower motors or heater blowers. They rarely even flow more CFM than is flowing into the throttle body, actually creating worse performance. The few that do flow more, still have problems compressing the air, essentially doing nothing at all. There are some that are not completely false, they are well over $100 US and only make about 1-3 (They claim a but more, and I'm sure that in perfect controlled conditions it's possible) extra HP after the load put on the electrical system.