Apparently they are supposed to improve the earth return of all electrical loads therefore making the car electrics more efficient ie. better throttle response, brighter lights, clearer audio etc. etc.
But to be honest unless your wiring or terminals are all corroded, you should be ok.
A lot of people install these kits for engine dress up purposes, myself included.
Someone might have had positive results but i didn't detect much difference, maybe a slightly smoother idle.
Hope this helps.