grounding give ur car a lower resistance n therefore improving de electricity flow in ur car... so will get brighter lights, more bass from ur ICE n some other minor changes...
voltage stabilizer is to give ur car a constant voltage to supply to all de electrical items in ur car... all cars have fulctuating voltage due to de alternator.. so with this aftermarket voltage stabilizer... they claim it can make ur light brighter, better sound quality from ur ICE, smoother engine n more power...
well.. i have grounding in my car.. n it works for me.. most obvious difference is de bass improved n no dimming of lights at light during idle..
then later i made my own DIY VS(voltage stabilizer).. n installed it.. i got even more bass.. no dimming of headlights.. engine got more power.. n de aircon seems cooler.. duno y....
btw.. i'm selling de VS i mentioned above(i manufacture n sell - much cheaper than after market ones)... anyone interested can contact me.. ;)