Let's say LT's to a Y to the intermediate to one big cat with a sensor before and after the cat and flanges after and before the sensors to replace with a straight pipe after inspections. Is this worth the trouble or what combos should I go with.

 

you have to have one cat per side. one cat wont work. it will also throw a code if the cats are too far from the headers because they wont get hot enough. if it throws a code, then it will fail inspection also. i had already asked this question to my buddie who is an inspector.