I would assume most performance vehicles have a problem with intercoolers not operating efficiently enough but Ford actually designed the Focus RS in a way where its intercooling system was operating too well. So much so that they had to rummage around the Ford parts bin for a blanking plate to reduce its efficiency. The blanking plate you see in the in the picture above? That’s actually from a diesel Transit van with a different intercooler that just happens to have a plate that fits.
During the Focus RS’ development program Ford discovered that in areas with high humidity the RS’s very capable cooling system caused water vapour to collect in the intake tract. This collected vapour inside the engine will turn into water and nobody wants that. To reduce the intercoolers efficiency by a slight margin, Ford’s vehicle engineering manager, Tyrone Johnson, managed to find a blanking plate that is dimensionally perfect and it just happened to come from a van. Why create a new piece if a plain jane part from another vehicle will do the job? It’s more expedient and cost effective this way.
For anyone thinking about removing the plates to increase the Focus RS's performance, you'd be wasting your time. The blanking plate does not reduce the Focus Rs' performance in any way and removing them will not increase its performance either.
So now you know, in the words of Alex Kersten; “the Focus RS is part Hoonigan, part van.”
You can find a video of this whole discussion between Alex and Tyrone on
How Ford 'Fixed' The Focus RS's Intercooler After Discovering That It Was Too Cool