Can anyone educate me as to the purpose of what appears to be an extra valve stem hole in an OZ wheel from a 2002 IRL car? There is a normal valve stem hole towards the outer edge of the wheel, but then there is a second hole, 180 degrees around the wheel, but very close to the middle of the wheel centerline, drilled not tapped. Sorry I don't have a picture. Three of the four wheels I'm restoring for a display car have this hole plugged with a nut, bolt and gaskets, but the fourth one is missing and I don't know where to get another plug. Can anyone point me to a source for these plugs? I'm also curious what the original purpose was for the hole... pressure relief valve, pressure monitor? Thanks.