Todd has it right. The parts diagram is just going to confuse you.
A 1997-1999 2.5 is different than a 2000-2004 2.7/3.2. Then you have ROW cars which are different then our cars. The parts diagram jumbles everything together in one diagram.
This picture is a North American 2.7/3.2. There are 2 cats on each side, for a total of 4.
The first or starter cat is part of the exhaust header. There are 2 sensors on the first cat. There is another cat before the muffler but it has no sensors. This is for one side.
Then you repeat for the other side of the car.
