What excatly will a new pully do for a stock Z-tec? Will there be any noticable diff.?

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1997 Ford Contour GL (Pacfic Green)
2.0 L. 4 Cyl. Z-Tec
2 Rockford 12' subs & a 600watt Rockford Amp


1997 Ford Contour GL (Pacfic Green)
2.0 L. 4 Cyl. Z-Tec
Aftermarket Foglights
2 Rockford 12' subs & a 600watt Rockford Amp