the intakes are not blocked. There is a polystyrene piece behind which is the support for the bumper and then a massive metal frame behind so if they were open it goes to nowhere.
If you look close at the front grills they have fins that direct the incoming air upwards. So if you look at your car Ferdi the 'hole' will be open at the top.
Dont forget on these cars the radiator is cooled from the air dam under the front f the car not the gaps in the bumper. The bumper gaps let air up into the engine bay and roughly towards the air intake. However this is not worth anything power wise etc.
If you do the cold air intake mod which involved cutting out the under tray of the air intake then you get a ram air effect with the air from under the car directed by the air dam. I've had a notiable benefit from this
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'99 Z28 A4, 253 LS2 heads, 228R TSP cam, Patriol Dual Springs, Double roller timing chain, LS6 ported oil pump, OBX LTs, 3" True Duals, LS6 intake, 42lb/hr injectors, SLP lid + bellow, EFIlive COS 3 Speed Denisty Tune (self tuned), 3200 Circle D stall, CAI mod, KYB AGXs, Eibach Pro Front Springs, UMI panhard, LCA + Brackets, Strut Brace, Custom Subframe connectors, WS6 axle with 3.42s, 18" American Racing Rebels, US mirrors, 93 tail lights, 3.5 inch custom cowl hood. Mickey T's Street DRs on Vette-ZR1 wheels for the strip !
Best ET: 12.0 @ 116 mph (on a 0-60ft of 1.8 s)