Why 3 cats?

Alright why in the world does my 1997 GT have 3 cats on either side on the stock pipe?? Seems so retarded to me. How many cats do the newer GTs have? No wonder these cars can't breathe. How much HP can I expect with a PI intake and a catted H/X pipe get me about?
 
I think bbk claims about 8-12 hp for a catted x, and I've seen posts saying the pi intake gets as much as 20 or so. I plan on getting the intake and gears soon. The intake is supposed to be a drop in replacement. I live in florida(no emmisions tests), so I cut off all four of the cats and put on two high flow cats, and cut out the h and put in an x and I have a catted x pipe for half the cost of a new one. Sounds good without being annoying. :)
 
Yep, damn POS's
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Get a mid pipe and let imports hear what a real car sounds like.