If you are talking about the black stripe on the drivers side below the head light area. That is were the Manufactures nose model number is, and NASCAR requires this not be painted or covered so they can verify the nose piece is the correct one. This is the same number that NASCAR looked at when Robby got fined for running the wrong Dodge nose last year. I dont remember the spacifics but the serial number on the Dodge nose RGM was given ended with a B and the nose the Dodges should have ended with an A.
Sorry to disagree guys but those are oil cooler vents. They usually only have them on the car at superspeeday races. Some teams don't use them at all. Check it out.