The front cooling architecture of C5-R's is kind of an interesting puzzle but it changed a few times over the years. Like I always kind of wondered what the fuck they did with the big engine air intakes beside the fog lights when they had tiny air restrictors and this is the first time I've seen the mesh fenced part on the inside was also feeding the radiator. I can't even tell on this car which duct actually feeds the airbox and which is the brakes, and even more oddly it has the 2000-2001 NACA duct beside the headlights mounted even though this is a 2002 chassis which was upgraded to 2003 bodywork. Seems like that was actually feeding the air restrictors though. Maybe the European team running it ran out of 2002 parts and had to use somebody else's older spares.

So my broad guess is that the 1999 cars had engine air and brake cooling in what would be considered the stock locations, the 2000 car moved the engine air to hose new ducts and the brake cooling to the "engine" ducts, and the 2002 cars likely shifted the air restrictor intakes to the splitter beside the rad ducts and they added some secondary brake ducts or something to the outer splitter in 2004.