Most Fiesta's came with the under bonnet sound deadening, however it wasn't included on the ST due to the heat buildup from the bigger engine - plus the fact that it rested on the airbox when the bonnet was shut.

I think it'll fit but will be tight with the standard airbox. If you've got an aftermarket filter, take the box off and the sound deadening should fit better but I'd definitely still keep an eye on under bonnet temperatures.

It was on the diesels (tdci's) due to the noise, and the Ghia's AFAIK.