Kostas, in principle they will work, but it is like anything to do with the combustion engine. Increases in power without an increase in efficiency requires more fuel. 
With todays adaptive ecu's the benefit will last for a very limited time inly.
To anyone looking for more power I would say the following.
Very regular maintenance. A healthy engine is an efficient (relatively speaking of course).
Make sure your tyre pressures are spot on.
Look at what you don't need to carry in the car (don't throw the spare wheel!).
Dave, I agree with most of your theory, but on a IC engine there are 3 efficiencies the Volumetric the mechanical and the combustion efficiency in any engine that you optimise the fueling and timing characteristics you improove the combustion efficiency, i'm not saying that the cheap resistor is an accurate optimisation tool but if you could achieve something if you were very caefull with the way you implement it.
Or just maybe the well paid engineers that spent several years and millions developing the car did a fair job. There are ways that you can make small gains, but fooling the ECU is far from the right way to go about it. The only simple sure-fire solution is to make sure that your car is in proper condition.
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Topic: What's the catch? (Read 2932 times)