...is It Even Possible To Have This Combo And Still Pass The Sniffer Test Here In Cali From Experience??....as Far As The Visual Goes, Some Places Won't Be Able To Tell The Difference Anyway...just Really Concerned About That Sniffer Test...

 

I highly doubt you will pass. The design of the headers and y-pipe will force you to weld the cat at the tailend of the y-pipe, placing it far away from the hot exhaust gases that are passing through the headers. The cat will not be able to heat up as it should and its efficiency will be far less.