Although just about good enough for a standard engine, the Fiesta ST's standard airbox can be found lacking when the power levels have been pushed up by a re-map and other modifications.
To get the most from your Fiesta, ITG have developed a new intake. The filter is mounted down behind the bumper, well away from any power robbing heat under the bonnet.  Aside from the increase in power, there are improvements with throttle response and a pleasing, yet unobtrusive increase in intake noise.
Testing has shown gains of 15hp using the ITG kit over the standard airbox.