I also like one advert that claims it extends engine life
The electric ones will improve power at lower revs but haven't got the power at higher revs. I am surprised nobody has brought out a hybrid system, electric and pulley driven, as each counteracts the other's shortcomings but turbos seem to be the order of the day.
I wonder if anyone has come up with an active exhaust extraction/decompression system? Turbos must increase the pressure at the exhaust, this is an inefficiency which must be similar to the power required for a supercharger.
I laughed at another gimmick where one was powered from the vacuum line - this would mean you were extracting air from the vacuum line and then pumping air in before it, overall this has got to lose power not gain, alright if you just want a "shiny" under the bonnet but no good for Santa Pod.