Have any of you guys ever used/have one of these in your car? If so what do you think of them, ie Do they make any difference? This is an ad that I found and was wondering if anyone here has one and what are their thoughts on it. "Voltage Stabilizer regulates the voltage of the car's electrical system, providing constant voltage at all times. Normally the electrical system's voltage will fluctuate under acceleration resulting in power loss and rough power delivery. The Power Voltage Stabilizer eliminates this voltage fluctuation, providing a constant voltage, thereby smoothing power delivery and optimizing power. Low rpm performance is improved noticeably, with improved response, acceleration, and smoothness. Fuel economy is also improved, especially for city driving conditions."

Just another gimmick I've seen. Sounds like a big capacitor in a box to me.

your alternator already does this.