I have a 318is and am planning to get twin DTM's at a very good price. However, the rear bumper valence opening (where the exhaust tips come out) is narrower on the 318's compared to the 325/328. I was planning on cutting the opening to a larger diameter but was curious as to how much larger the opening is on the 6 cylinder BMW's. Could someone measure the width of that opening to give me an idea of how much I would have to "shave" off? I know I could buy a new valence and just replace mine, but the one on my car is painted and I don't want the hassle of having to repaint another one. Thanks a lot.