Ford: Catalyic Converters, native oregonian, flow cats

Question
I'm a native Oregonian who moved to California about 2.5 years ago.  The car I brought with me passed it's first smog, but failed the second one.  The place I took it to for it's second smog said it failed it's visual inspection because I was missing my two lower cats (I guess my car is supposed to have 4, and the first place just overlooked it).  It's a '89 Mustang GT, btw.  But it passed the emmissions part just fine.  Why is a visual required if it passes the pollutant part?  And is my car really supposed to have 4 cats?

Answer
they are wrong as long as your co's and no's pass which is what your car puts out then it doesn't matter along as it passes.you could always tell them they are high flow cats.now the other thing if they still hassle you then go to the junk yard and get yourself some cat shields and weld them in and they will never know the difference