You need to remove the cams to replace the variocam rails. The variocam and cams come out together. I'm guessing that on a 99 the rails are well worn if the car has any amount of mileage on it. Here are variocam rails that I took off a 2002 yesterday (95k miles). You can see the significant wear-the wear pads should be smooth. The wear pad on the other side of this variocam was worse.
