for one it's not a 12 ounce differance it a 6lbs differance
the Esslinger pulley is the LIGHTEST UDP avaliabe for the Zetec

and this is all I am gonna say on this since some people seem to think they know how something works at which they don't even have.

2003 Subaru WRX some mods Even if you don't have the answer, you certainly have to admire the problem. aka ZetecRacing