Is your '03-'04 Mach1 rpms not returning back to idle fast enough?
 These restrictor plates makes the rpms drop back to idle faster like a carbureted motor.
 
 Made of .027" laser cut stainless steel.
 These plates have a 5/16" hole.
 Larger holes can be requested.
      Fits '99-'04 Mach 1 & GT Mustangs.
     $12 each
 
Here is more discussion on restrictor plates at Mach1registry.com
No. 1 topic.
No. 2 topic