because for the price you pay you dont have much more performance and you dont have much more of the nice sound of a open air filter

1998.5 Toreador Red/Midnight Blue Contour SVT - #5912/6535 - DOB - 05/11/1998 - RU-3530/CTA Intake Pipe MSDS Heaser/Y-Pipe Magnaflow #10435 9mm Ford racing SPEC Stage one/Spec Alum. Flywheel HERE