Originally Posted by jimandmandy
The "theory" that modern EFI cars are running rich all the time is just plain WRONG. They would never pass smog if that were the case.
A catalyzer can easily smake a rich (though not overly rich) engine pass smog.
All modern engines are set from the factory to run lean-of-peak
You mean slightly on the lean side? Do you have any reference to that?
A "chip" can be just as phony as fuel line magnets
A fuel line magnet can not possibly have *any* effect on mpg, while the 'chip' can. Of course, the effect can also be bad, which is the case with many gas saving devices.