If it both gave more power and increased fuel economy, I think the car companies might be using something similar, no?

Be wary of such "upgrades." As other posters have said, it makes things run very rich which is not good for your engine, exhaust system, or economy. It will give a bit more power though.

If you want horsepower, there are better ways, but rarely do they cost $20...of course, clean airfilter, new plugs, and other tuneup parts can often gain lost hp.

Good luck,

Nate

--
1997 850, 1979 242GT, 1990 740GL