I think he is referring to the 4.4i which has one "exhaust can" on each side but with dual tips at the end. Actually, on all X5s, there are two pipes running from the exhaust manifold all the way to the rear "cans" on each side. He is disappointed that it is not a true "quad" exhaust.

If you look at the M5 and M3, it is the same setup.

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