(Cheap from ebay) Magnetic Fuel Saver

[sternz]

Has anyone used one of these? If so do they really make any difference at all, or are they just a waste? I was just browsing on ebay and noticed these.

this is part of their description;

1) Powermag: Magnetic Fuel Saver can help engine to burn fuel more efficiently
2) Powermag: Magnetic Fuel Saver let your car run more miles per gallon
3) Powermag: Magnetic Fuel Saver will improve engine performance
4) Powermag: Magnetic Fuel Saver will reduce emissions
5) Powermag: Magnetic Fuel Saver will clean air

Magnetic Fuel Saver gadgets increase combustion efficiency for a cleaner burning engine. This reduces harmful emissions while increasing engine performance.

Benefits of Magnetic Fuel Saver
1) Save fuel, save $$, more MPG (miles per gallon )
2) 50% reduction of carbon monoxide and hydrocarbons
3) Helps pass emission testing/smog check
4) High octane performance with lower octane fuel
5) Improved performance - quicker starts
6) Stops scale build-up and corrosion in engine
7) Reduced wear on O2 sensor and catalytic converter

Any info is welcomed! Thanks in advance.