Upgrading to an aftermarket air intake on the Focus RS can result in noticable noise from the turbo housing, caused by air blowing across the OE resonator. This Revo Sound Supressor simply replaces that component and eliminates the resonance that causes the noise.Prevents aftermarket air intakes exacerbating whistling noiseEasy to fitReliable and durableThe turbo on the mk3 Focus RS can whistle under light load. This is due to the design of the OE resonator component on the OE turbo. This can become especially noticable if you fit a more open intake design, as the original airbox does a lot of sound dampening.This Revo Sound Supressor is a very simple fix for this problem. Replacing the original resonator with this improved design featuring a silicone cap acts as an active sound cancellation chamber, totally deadening the turbo whistle.