On mine (2001 3.0i) the 2 post cat connections are under that cover, and the 2 pre cat ones are mounted in plain sight on the left side of the engine (if standing in front of X) The 2 post cat wires travel down the rear of the engine, through a few little clips on the way down (1 accessible from top all the way to the back of engine bay, and two accessible from underneath by following the wires up with your hand almost to the point where it gets too tight for your hand to follow it any further). I just used a 22mm Craftsman Crows Foot Socket from Sears, and they came right out. They're anti-seized at the factory (or so I've been told) but regardless they came right out.

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