are you talking about a electric fan clutch? or electric fans?
I put electric fans on my old s10 blazer and had allot more power and better gas mileage, however I had a problem of the truck getting hotter in traffic, the electric fans don't seem to work as well.
I was toying with the idea of electric fans on my 4-runner but since the stock cooling always works great I ditched the idea
as far as a electric fan clutch I heard they failed more than worked