Costing from £1225 for the Focus ST upgrade and £599 for the Fiesta ST, and taking under 90 minutes to install, the upgrades significantly improve power and torque on both models.
The Focus ST upgrade - which includes a cast alloy inlet duct, high-flow air filter and a larger intercooler - boosts power from the 2.0-litre EcoBoost engine to 271bhp, while torque is improved to 295 lb ft. The upgraded car can sprint from 0-62mph in less than 6.0sec, more than half a second faster than the standard Focus ST.
Upgrades for the Fiesta ST - based around a remodelled air box with a new secondary inlet duct - improve power to 212bhp and torque to 236 lb ft. Sprint time for 0-62mph falls to 6.7seco, compared to 6.9sec on the standard car.
Both upgrades can be applied from 120 Ford-appointed Mountune dealers.