These are 2 different PS enhancement gadgets being fitted to my Myvi since a few years back.
At first, the Battery Power Stabilizer was fitted to improve the power supply for whole car usage, and i notice brighter dash board lighting, better idle speed, and some others power accessories can feel better!
After short time, the Speed-Syndicate guys also suggested the Fast-Road type Brisk Spark Energizer to increase more energy (mj) to the coils..
At all round rpm, my Myvi measured a +12.95v at its input wire & measured +16.65 volts at the PS output wires feed to all 4 coils with voltmeter.
By dairy use of this car results in much better engine power with less fuel consumption.