I'm not quite sure what you mean by obscure lingo... The part is called a 3-way catalytic converter. There are 4 cats in our cars, two in parallel up front after the exhaust manifolds, the 3-way that merges those two pipes together into one and a forth behind it. I think the part is unique because it, according to my dealer, does not match the normal Crossfire's and Mercedes faxed me a full compliment of exhaust parts diagrams for the SLK320 and SLK32, as well as one for the C32. The two AMG cars that share our motor have 4 cats, but they have two pipes with 2 on each pipe. The 320 has a 3-Way in the rear of the car, before the muffler, but it doesn't look like it would match either since it is off-center and is asymmetrical. I suspect that this Cat is "unique" in the way that our dashboard is unique; they lit it with green lamps and wrote SRT on it. This is probably the normal 3-way with a different flange or something... Agreed with the nut holding the wheel thing.