Change one to flow more CFM, boost goes down if the flow is above the max speed of the Vortech on the current pulley. Ahhh, me learn too! 
1999 Amazon Green SVT Contour (#554/2760)
Stock SVT Duratec V6 with:
Intake- K&N filter/75mm MAF meter
Exhaust- MSDS Y-pipe/Bassani catback
Durability-Ford "dual mode" damper, Mobil 1/K&N oil filter
179.2 FWHP at 6900 RPM
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