^ its simply older tech. and frankly a lot of the older roots style sperchargers arent that hot of a setup. they do ahve limited power. and the only good thing about them is mechanical simplicity.
the vortech centrifugal you had to mess with power steering lines to make fit (dangerous since hte power steering line is near the exhaust manifold on a zetec)
the only good supercharger kit (and the only one still being produced new)
is the procharger setup. which is a rather pricey thing considering you get no tuning.
i myself am procharging my svtf this year, mainly i got a good deal on the kit (used) and its a good way to learn about forced induction.
my next car will be turbo because lets just face it. turbocharged 4 cyl. engines are just better.
part of an army of freaks. but you still love me.