I was wondering if any of you had run into this same problem with you BMW's. Mine is a 2002 BMW 325i. Basically what it is doing is, when I maintain a steady speed below say 50 or so, whether in cruise or not, it drives normal but then if you watch the tachometer, it rhythmically drops about 400 to 500 rpms all of a sudden and jumps back up real quick, and keeps doing that over and over again really close together until I rev the engine or change speeds. You can also hear the engine rev lowering and raising with the tachometer, so it isn't an instrumental malfunction I would imagine. If anyone has any clue what is happening and what needs to be done, please let me know.