Ok, I just looked in the ESM. According to the ESM, the extra 2 cats were only on California models in 2000. I oculd not find a picture of the stock manifold. However, I was just poking around under the hood today and I'm 99.99% certain that the cats attach right to the end of the headers. The SLR has the spot for the pre-cat oxygen sensor which seems normal and then the cats would attach and then you'd get the next section of pipes with the rear oxygen sensor.