https://passionford.com/forum/techni...ir-intake.html

this is untrue.
with the fiesta st150 they have added a restrictive airbox to keep the power down, and a k&n kit adds a fairly decent amount of power.
same applies to the flexi pipe before the cat, again, restrictive.

just thought this should be added as this post leads it to believe its the same with all fords.