That rev-chip won't do anything for your car except end up causing some sort of damage. All it is is a resistor that changes the readings going into the ecu and will make you car run lean. If there was any such thing as a cheap $25 dollar "chip" that just replaces a sensor to give you more hp, then the sensor probably wouldn't be there in the first place.
As far as "cheap hp" there is no such thing... There are things you can do that will add a bit of power, but nothing major... Such as removing the resonator off of the intake tubing and such.